7-2 UVSOR の点検評価 - 分子科学研究所

7-2 UVSOR の点検評価
7-2-1 Adam Hitchcock 教授
_________________________________________________________________________________________ 原文
Review of Beamlines and Science at UVSOR
1. Overview
I was asked by the Director General to review the present status and future directions of science using UVSOR from the perspectives
* international activities
* application to molecular science
* in-house contributions and challenges in the area of molecular science
My comments are based on the recent (2010, 2011) annual reports and a series of nine one-hour sessions with UVSOR researchers
and UVSOR users from other departments in IMS and other institutions. I thank all the presenters for the careful work they put into
their presentations, which allowed me considerable insight into the present status and future directions. I was particularly struck by
the relative youth and enthusiasm of many of the presenters which speaks well for the vitality of UVSOR and IMS.
Here I make selected comments on each presentation / area of research / status of the instrumentation. After that I make some
general observations on how these current activities position UVSOR relative to other facilities with strong research programs in
molecular science, and where I think there are opportunities for improving international participation and enhancing the relevance
of UVSOR research to the overall mission of IMS, which I take to be primarily fundamental research into systems and phenomena
where the perspective of the molecular unit is a strong organizing principle.
2.1 Facility and Light Source Research (Masahiro KATOH, Director, UVSOR)
The synchrotron source, after updating to UVSOR-III in early 2012 (this year!), is a very competitive facility relative to all other
sub-1GeV SR sources. The most recent upgrade has significantly reduced the emittance and has freed up space for additional insertion
devices (total 6). This has provided an opportunity for adding a new, very competitive beamline for science (BL4U, STXM), a number
of other beamline and end-station upgrades, and conversion of BL1U into a very versatile platform for advanced light source generation
experimentation. The latter is an important aspect of a synchrotron facility as it provides ongoing challenges for the accelerator group,
opportunities for collaboration with other accelerator light source facilities, and can lead to large improvements in light source
technology, which may be a platform for a future upgrade of UVSOR. At the same time there appear to be too many challenging
initiatives under way—free electron laser development, coherent THz systems, fs slicing, and laser Compton gamma ray generation.
It was not clear which of these had priority or which had a potential or actual user community. The latter should be an important
principle in guiding priorities for further investment and development in this area.
It was noted that some beamlines have challenges with operation in the current top-up mode. The fraction of the time devoted
to top-up injection, and thus perturbation of the storage ring is 20% (12 seconds each minute), due to rather short lifetime of the
electron beam just after the upgrade to UVSOR-III. The present 12 seconds (12 injections) per minute seem long relative to those at
other SR facilities. The number of top-up injections will decrease as the electron beam lifetime and the injection efficiency improve
as in UVSOR-II. Efforts should be made to improve the top-up injection procedure, as soon as possible, not only to reduce the fraction
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of the time, but also to reduce any perturbations of the beam position or size associated with the top-up. This is particularly important
for brightness dependent experiments such as STXM.
2.2 Spectroscopy of Liquid Systems (BL3U: Masanari NAGASAKA, KOSUGI Group, IMS)
The liquid spectroscopy instrumentation developed at UVSOR is better than versions I have seen at the ALS and CLS. This is a
very rapidly developing area of SR science with tremendous potential for both fundamental and applied studies. The cluster apparatus
on BL3U is also an outstanding piece of equipment. Together with the gas, liquid and solid spectroscopy capabilities at BL3U and
other UVSOR beamlines, the ensemble is ideally suited for systematic studies of the evolution of structure (electronic, magnetic and
geometric) from isolated molecules/atoms, to the solid state. The session on cluster and liquid spectroscopy at the recent ICESS-12
meeting (St. Malo, France, Sep. 2012) was one of the best of that conference in my opinion.
The plans that Nagasaka outlined to extend the methods to in situ electrochemistry, liquid–solid interfaces; solid–gas interface
and in situ chemical and photochemical reactions are very exciting and will be some of the outstanding research from UVSOR in
the next few years. This area should be supported fully. There is also very strong synergy between these spectroscopy studies and
science with similar goals but with lateral spatial resolution, that will be performed on the BL4U STXM, which should be operational
and open to various classes of users by spring 2013.
2.3 VUV, EUV and X-Ray Absorption and Photoemission Spectroscopy of Solids and Gases
BL2A (double crystal monochromator) provides the highest energy photons at UVSOR. Despite being non-competitive relative
to similar BL at other SR facilities, due to the low critical energy at UVSOR, it operates well and has a small but steady use by a
number of Japanese research groups, primarily for materials science using X-ray absorption. It was noted that the publication rate
was low which may reflect the non-competitive nature of this beamline. For a low energy ring like UVSOR a better choice to cover
the high energy range would be a grating monochromator, which, with suitable multilayer mirror technology, can provide quite high
performance up to 3–4 keV.
BL5B features an unusually wide photon energy range (6–600 eV) and a very large chamber equipped with a very flexible 6-axis
goniometer. It is apparently one of only a few beamlines in Japan that are capable of characterizing large optical elements in a very
flexible way. The research carried out on this beamline is primarily of a service character. At other facilities (e.g. ALS BL 6.3.2),
there are active research programs in developing coatings and characterizing optics for semiconductor EUV lithography. This could
be an area for future research at BL5B.
BL4B, the first soft X-ray beamline at UVSOR with high energy resolution, has produced some high quality molecular and
materials science in recent years, based on research by in-house and external users. The newer BL3U undulator line covers a similar
energy range and is now the preferred beamline for spectroscopy research in this energy range. However BL4B still has an active
research program in magnetic materials (see discussion of the presentation by T. Yokoyama in section 2.7).
BL6U is the most modern and competitive of the beamlines supervised by Shigemasa. Its variable angle, variable line spacing
PGM monochromator provides good intensity with outstanding energy resolution. It was noted that the minimum undulator gap that
can be achieved at present is 13 mm, whereas the design specified a 10 mm minimum gap. The reason for this should be identified
and repaired if possible, since there are some photon energies that cannot be reached due to the out-of-spec minimum gap. The two
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end stations for BL6U are each internationally competitive. The gas phase Auger electron photoion coincidence (AEPICO) apparatus
is ideally suited for studies of molecular photoionization dynamics with high energy electrons, and complements research at other
facilities which use the Cold Target Recoil Ion Momentum Spectrometer (ColTRIMS) approach. The MBS-A1 photoemission end
station is also very competitive internationally and has been adapted for two-dimensional electron spectroscopic studies in gas phase.
Consistent with its competitive character, there are a number of outstanding international collaborators (Lablanquie, Simon, Piancastelli)
using this instrument.
The gas phase examples presented by Shigemasa, along with those in the 2011 UVSOR annual report are excellent examples of
modern synchrotron based molecular dynamics and photo-physics science. I particularly admired the studies of ultrafast dissociation
in C 1s excited CF4 (p. 53) and the electronic Doppler result in S 2p excited OCS (p. 56). BL6U is one of the outstanding examples
of molecular science research at UVSOR and should continue to be well supported. Identification of suitable collaborators and
independent researchers from the international community should be a target for increasing the international visibility of the molecular
science program at UVSOR.
I note that Shigemasa and his group members are now using the SACLA X-ray free electron laser for advanced molecular
photophysics studies. This is a very good development for UVSOR. Opportunities of using research at UVSOR to complement
SACLA research, possibly resulting in joint publications, should be encouraged.
2.4 X-Ray Absorption, X-Ray Emission and Angle Resolved Photoemission of Solids
(BL3U, BL6U: Hiroyuki YAMANE, KOSUGI Group, IMS)
BL3U is a world class facility for X-ray absorption, X-ray emission and resonant X-ray scattering. This has enabled some
exceptional research by UVSOR and outside researchers. The examples of XAS characterization of organic conductors and
semiconductors for organic LED, organic electronics, and organic photovoltaic systems were fascinating. I draw particular attention
to in operando measurements which used the difference of FY_NEXAFS spectra induced by applied potentials or currents to
characterize the changes in molecular structure of electronic states (PRL 107 (2011) 147401). This is one of the first in operando
soft X-ray studies of a device material to my knowledge. It revealed the surprising result that the electronic structure changes are
associated with σ states, rather than the π states normally believed to be involved in the conductivity of organic conductors and
semiconductors. These results have important implications for the field of single molecule electronic devices, which is a very hot
topic and target of development at many research facilities around the world.
The X-ray emission spectrometer has exceptional performance relative to similar facilities at other SR centers. The energy
resolution is below 100 meV at 140 eV X-ray energy, which is very competitive. The efficiency of the novel transmission grating
spectrometer is probably the highest in the world for soft X-ray spectrometers. It has been used for studies of a number of interesting
systems, including DNA polymers (poly(G-C), poly(A-T)) and N-doped graphene nano flakes (J. Phys. Chem. C 116 (2012) 16251).
The higher performance transmission grating which is planned for the XES spectrometer will further improve energy resolution and
possibly efficiency. The future plan to apply XES and RIXS techniques to in operando studies of molecular devices is really at the
cutting edge of international SR science with X-ray emission spectroscopy.
An outstanding program of angle-resolved photoemission from molecular solids and thin films on BL6U was also described by
Dr. Yamane. The system for these studies is one of the best in the world, achieving < 5 meV overall energy resolution (photon &
electron), ability to cool to 13 K, and a 5-axis motion system that allows rather complete band structure studies with the sensitivity
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needed to track band dispersion in organic systems which are typically much smaller than the dispersion in semiconductor and metal
systems. The achievement of these technical capabilities in an instrument constructed at IMS is a tribute to the excellence of the
Equipment Development Center which is a real asset for UVSOR and IMS. The quality of the preparation chamber and its ability to
allow for preparation of organic thin films in a system also used for semiconductor and other samples was noted. There is strong
international participation on BL6U. A number of interesting examples were outlined, including: Band alignment at the interface
between carbon nanotubes (CNT) and a SiC substrate in CNT rafts prepared surface decomposition of SiC (Maruyama); spin–orbit
(Rashba) band splitting in 1-d Pt nanowires (Yeom); nanoscale phase separation in DNA Watson-Crick (G-C) multilayer films
(Friedlein); and valence band dispersion in metal phthalocyanines (Yamane). The latter project, a major effort by Dr. Yamane, showed
very fascinating temperature dependent dynamics results which gave important insights into intermolecular interactions and how
these can be tuned by adding substituents to the phthalocyanine or changing the metal. Since the molecular films which are the focus
of these studies are easily damaged by synchrotron radiation, it is essential to be able to prepare very uniform samples which can
then be used to circumvent radiation damage by scanning the sample to fresh areas during the measurements. This system is one of
the best in the world for ARPES studies of organic solids.
Dr. Yamane identified a number of improvements that could be made to further enhance the performance of this facility. These
include a larger analyzer (e.g. D80 VG Scienta) to improve efficiency; a new analysis chamber; and addition of an O2 dosing system
to remove carbon contamination on the BL6U optics. To the extent these will facilitate new molecular science, UVSOR/IMS should
seriously consider these requests.
2.5 Scanning Transmission X-Ray Microscopy (BL4U: Takuji, OHIGASHI, UVSOR)
BL4U is a new soft X-ray undulator beamline with a dedicated STXM end station. STXM is a relatively new spectromicroscopy
technique which has may applications in both fundamental and applied science. The planned science program is very ambitious.
Further development of the instrumentation and techniques (cryo spectromicroscopy, cryo-tomography, ptychography) will require
substantial effort, and should be staged after reliable basic operation is achieved. The STXM project at UVSOR will have a significant
advantage relative to other STXM facilities, as IMS is able to provide on site sample preparation (ultramicrotomy, focused ion beam
milling, high end optical microscope with encoders and micromanipulators, etc.). BL4U & the STXM end station are part of the
Nanotechnology Platform Project in Japan. This is very appropriate and will link the STXM to the on site analytical transmission
electron microscope (TEM), which is an excellent complementary research tool. The presence of scanning Raman and IR microscopes
(both lab and UVSOR based) provide additional complementary analytical microscopy techniques. Efforts should be made to facilitate
multi-technique studies, for example, by developing sharable sample mounting and methods to quickly locate the same spatial regions
of samples in the different microscopes.
2.6 Solid State Science (BL1B, BL5U, BL6B, BL7U: Shin-ichi KIMURA, UVSOR)
BL7U and BL5U, both dedicated to angle resolved photoemission (ARPES) of surfaces and solids, are the 1st and 2nd most
popular beamlines at UVSOR, as judged by usage, ratio of allocated to requested shifts, and numbers of publications in high profile
journals. BL7U is among the very best facilities world wide for condensed matter electronic structure studies using low energy
photons. Usually researchers turn to beamlines with higher photon energy (>100 eV) if they need additional sampling depth to ensure
they are sampling bulk properties. At BL7U very low outgoing electron energies are used, as these are also bulk sensitive. The energy
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resolution of 2 meV (electron and photon combined) is only surpassed by a few other lines in the world. The Apple II insertion device
means that the full polarization properties of samples can be explored. A range of outstanding condensed matter science is taking
place on BL7U including: Detailed studies of Fe-based superconductors; exploration of charge density wave effects at the surface
of graphite; investigation of organic conductors. The ongoing development of conventional optical focusing techniques for UV light
to achieve sub-micron spot sizes in the 7–9 eV photon energy could lead to some world-unique capabilities which would complement
higher photon energy nano-ARPES lines at the ALS (Maestro) and Soleil (Antares). The potential for using such a facility to study
laterally heterogeneous surfaces was illustrated with a novel system of electronic phase separation which is suspected to occur in
κ-(Et)2Cu[N(CN)2]Br on the sub-micron spatial scale. BL7U should invite more international users.
While BL5U is a somewhat older ARPES system with lower performance, its higher photon energy range (up to 200 eV) provides
a useful complement to BL7U. Planned modifications to improve the performance of BL5U were described, including replacement
of the monochromator, which has a resolving power of only 3000, as opposed to the 10,000–50,000 resolving power of BL7U.
Although a number of organic materials are being studied with BL7U and 5U, the majority of the science is in the realm of condensed
matter physics of semiconductors, metals and correlated electron materials.
BL6B provides light in the IR and THz range. Kimura outlined some exciting instrumentation developments, including his magic
mirror which achieves exceptionally large angular collection of bend magnet IR radiation (only exceeded by the mirror array system
of the IRENI facility at SRC, Wisconsin), and the recent adoption of a focal plane array detector for far- and mid-IR spectromicroscopy
on BL6B. Interesting science using far-IR (THz) to study organic materials at high pressure was presented. However there has been
relatively little molecular science using BL6B despite the extensive use of synchrotron IR spectroscopy and spectromicroscopy for
molecular science at other SR facilities around the world. Given the activities in organic electronic materials and biosciences at IMS,
it would seem there is excellent potential to expand use of BL6B, especially in the mid-IR to visible range where many non-SR
scientists are actively using lab based IR spectroscopy and spectromicroscopy. I understand that Assoc. Prof. Furutani (Life and
Coordination-Complex Molecular Science, IMS) is interested in partly-dedicated use of BL6B for bioscience applications. The new
program to provide such ‘approved program’ time (outlined by Kimura at the end of his Friday presentation) seems to be an excellent
opportunity to increase molecular science activity at the IR microscope on BL6B. There is also a lot of science which can be advanced
using STXM and IR microscopy in a complementary fashion. Development of identical or cross-compatible sample mounting and
fiducialization approaches (perhaps linked through the encoded stages of the optical microscope at BL4U STXM) could significantly
facilitate that development.
BL1B has capabilities for developing novel coherent THz and THz-VUV experiments using laser slicing with amplitude modulated
pulse trains. This is very exciting light source physics with good potential to achieve new physics. Possible molecular science
applications of the coherent THz source were outlined in the areas of protein motion and carrier dynamics in Li ion battery and
organic Dirac Fermion materials. At present the motivation is clearly exploration of novel instrumentation/light source capabilities.
Its impact on molecular science is likely to be limited, at least in the short term.
2.7 Magnetic Materials (XAS, XMCD) (BL4B: Toshihiko YOKOYAMA, IMS)
The superconducting magnetic spectroscopy system on BL4B is a competitive facility relative to related systems internationally.
It has among the highest on-sample magnetic field at SR facilities and has a good degree of flexibility in sample mounting relative
to the field and photon polarization such that all aspects of the magnetic properties of samples can be measured. The facility is part
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of the Nanotechnology Platform Project in Japan, for which funding was recently renewed for a 10 year period. Professor Yokoyama
gave overviews of five specific research projects in the surface and thin film magnetism: Magnetic properties of Fe islands and
nanowires on W(110); Co nanorods on Cu(110)-(2×3)N; γ’FeN/Cu(001); Fe on Si3N4/Si(111)-(8×8); VOPc/Si(111). The latter is
the only example with a molecular science flavor. In this case, a combination of polarization dependent NEXAFS and V 2p XMCD
was used to determine the structure and magnetism. Although there was a significant change in electronic structure and bonding
between monolayer and multilayer VOPc, the V 2p XMCD magnetic signature was identical indicating the V 3d character is similar
despite the bonding change. All of the examples presented high quality data from very challenging low signal systems. While similar
science is being done elsewhere, Professor Yokoyama noted a major advantage of the UVSOR operation was the much lower time
pressure which allows for sufficient time to study samples requiring careful in situ preparation.
2.8 Photoemission of Organic Solids (BL8B: Satoshi KERA, Chiba University)
BL8B is a public beamline dedicated to ultraviolet photoemission spectroscopy and ARPES of organic solids. The presentation
gave a strong motivation for the research of the Chiba group in terms of the need to understand the fundamental principles of molecular
assembly in order to control electronic structure and functionality of organic materials for electronics applications. A quantum
perspective and the theme of wavefunction spreading was used to interpret recent results on: Weak band gap states in fullerene thin
films; conduction mechanism and hole-phonon coupling as a limit to charge mobility in pentacene films; band dispersion in rubrene.
BL8B is the oldest beamline at UVSOR. Plans to improve the instrumentation (replace the current analyzer with a modern 2D angleenergy electron spectrometer) and move from 8B to 2B were described and motivated by the need for higher performance to enable
use of UV-ARPES for momentum space orbital mapping of organic solids. This approach was highlighted by a number of presentations
at the recent ICESS12 meeting and is clearly a trend in international science in this area.
2.9a VUV Optical Properties (BL3B, BL7B: Shin-ichi KIMURA, UVSOR)
BL3B and BL7B are dedicated to studies of the optical properties (reflection, absorbance and luminescence) in the visible—and
vacuum UV regions. BL7B is an older beamline that has recently been reconfigured to focus on ellipsometry measurements. BL3B
has recently been moved from BL1B and significantly upgraded to the HOTRLU system which has greatly improved flux (relative
to the previous BL1B system), and a smaller spot size by using a Kirkpatrick-Baez focusing system. Research on the UV optical
properties of a number of interesting materials was described, including AlN and EBSTO, a layered organic–inorganic system, as
well as studies related to calibrating instruments for astrophysics. There is significant international participation and quite high
productivity (BL3B & BL7B generated over 20% of all UVSOR publications in the past 5 years), although the publications are rarely
in the first rank journals.
2.9b VUV Spectroscopy of Biological Molecules (BL3B, BL7B: Kazumichi NAKAGAWA, Kobe U.)
Professor Nakagawa described his program for careful transmission measurements on thin films of the individual amino acids
and DNA bases, which are used to generate absolute absorption cross-sections. Results are typically reliable to 5–10%, but often
only after a sum-rule normalization correction. The motivation for the work is UV biosensors, and connections to UV damage related
to cataracts. However there was no evidence for a direct link to those areas, and the energy range relevant to these issues is only a
very small part of the energy range over which the absorption was measured. However, in terms of understanding the fundamental
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physics and chemistry of radiation damage, such a wide range of spectral studies may be meaningful.
3. General Comments about Science and Future Directions for UVSOR
3a. International Competitiveness
As outlined in detail above, some beamlines, end-stations and research programs are more internationally competitive than others.
Of particular high quality I consider BL3U, BL6U and BL3B.
3b. Relevance to Molecular Science Mission
The liquids, electrochemistry, and chemical/photochemical reaction science, as well as the electronic structure (ARPES, XAS,
XES) studies of molecular thin films are areas of the most direct relevance to molecular science. There is a strong tradition of gas
phase spectroscopy studies at UVSOR which is very relevant to molecular science. However, I was less impressed by the instrumentation
and science in this area, than in other areas. Although not mainstream molecular science, the instrumentation and programs in
condensed matter electronic structure (ARPES) are very strong and definitely worth continuing.
3c. Role of In-House Contributions/Future Directions
A key aspect of UVSOR is that a large proportion of the scientific direction, instrumentation development, and beamtime is
determined by the in house scientists. This is in strong contrast to most other SR facilities, where it is the science and interests of
external researchers that is dominant. I consider the exceptional in-house research programs to be a real strength of UVSOR. The
quality of the science on the international scale then strongly depends on the quality of the team leaders, the researchers they attract
to their teams, and their international collaborations. IMS is fortunate to have some very talented researchers. Relative to other
facilities, the size of the UVSOR staff is very small, yet the output is outstanding, from the perspectives of quality, diversity and
quantity. Hiring of at least one additional faculty in IMS or UVSOR, at the professor or associate professor level should be (and, I
understand, is) a high priority. While the main goal should be to find a dynamic young or mid-career individual with a passion for
synchrotron-based research applied to molecular science, if there are equally good candidates, research in the area of nanoscience
would build best on the existing instrumentation and strengths of UVSOR.
November 22, 2012
Adam P. Hitchcock, FRSC
Professor of Chemistry & Chemical Biology
McMaster University
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_________________________________________________________________________________________ 訳文
UVSOR ビームラインと研究の評価
1. 概要
所長から UVSOR を利用した研究の現状と将来の方向性に関する以下の3項目について評価するように依頼を受け
以下のコメントは最近の2010年,2011年の UVSOR 年報(Activity Report)と UVSOR 所属研究者,所内 UVSOR
特に UVSOR 及び IMS の活力について十分説明してくれた発表者の若さと熱意に感銘を受けた。
したときに,強力な分子科学研究プログラムを持ってして,どのように UVSOR を位置付けるのか,また,国際参加
を改善させ,IMS 全体の使命に UVSOR をもっと適合させる機会がどのあたりにあるのかについて考えた。なお,
IMS の使命としてとりあげたのは,分子を単位として全体を見るという観点から分子システムや分子現象について重
2.1 施設及び光源研究(加藤政博,UVSOR 施設長)
2012年度の前半に UVSOR-III へと高度化された施設は他のどの 1 GeV 以下の放射光源と比較しても非常に競争力
この高度化により,研究面で極めて競争力の高い STXM(走査型透過軟X線顕微鏡)ビームライン導入を初めとする
多数のビームライン接続装置の高度化,BL1U ステーションにおける多様な光源開発及び利用実験が可能となった。
は,UVSOR の将来計画に結び付く光源技術として大幅な向上をもたらす側面もある。と同時に,あまりに多くの課
全体の 20% となる毎分 12 秒と多い。これは UVSOR-III に高度化された直後のビーム寿命の短さに起因しているが,
他の放射光施設に比べて長いように思われる。ビーム寿命及び入射効率を UVSOR-II と同等水準に向上し,また,入
これは特に STXM のような輝度を必要とする実験において重要である。
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2.2. 液体系の分光(BL3U:長坂将成,IMS 小杉グループ助教)
UVSOR で開発された液体の軟X線吸収分光の測定装置は,ALS(米バークレーの放射光施設)と CLS(カナダの
から大きな可能性があり,今,急速に発展している分野である。BL3U に設置されているクラスター装置も素晴らし
い装置である。BL3U や他の UVSOR のビームラインで気体,液体,固体の軟X線分光装置を組み合わせて,孤立分
近の ICESS-12 国際会議(2012年9月にフランス・サンマロにて開催された電子分光会議)におけるクラスターと
り,今後数年において UVSOR の中でも際立った研究成果になると思われる。この研究分野は最大限支援すべきである。
また,これらの分光手法と BL4U STXM で展開される面内方向の空間分解能を求める研究とは強い協力関係にある。
2.3 固体及び気体の VUV,EUV,X線吸収分光及び光電子分光
(BL2A,BL4B,BL5B,BL6U:繁政英治,UVSOR 施設准教授)
BL2A(二結晶分光器)は,UVSOR で最も高エネルギーの光を供給しているビームラインである。BL2A は順調に
ているが,UVSOR 光源加速器は臨界エネルギーが低いので,他施設の同種のビームラインと比較すると競争力はない。
BL2A の競争力の無さは,論文の出版率が低いことからわかると言ってよいだろう。UVSOR 光源のような低エネルギー
合せれば,3–4 keV まで極めて高い性能が期待される。
BL5B は,非常に広い光エネルギー領域(6–600 eV)と極めて自由度の大きな6軸ゴニオメータを装備した大きな
ムラインである。このビームラインで実施される研究内容は,研究の補助的性格のものが多い。他施設(ALS の
BL6.3.2 など)では,半導体 EUV リソグラフィー用光学素子のコーティング開発や特性評価において活発な研究プロ
グラムがある。このような開発研究は BL5B の今後のターゲットになるはずである。
BL4B は,UVSOR 施設における軟X線領域での最初の高分解能ビームラインであり,所内及び所外利用者によって,
近年,質の高い分子科学や物質科学の研究成果が出ている。今や,BL4B とほぼ同じ光エネルギー領域は新しい
BL3U アンジュレータラインがカバーしており,BL4B より分光研究に適したビームラインとなっている。ただし,
BL4B は磁性材料に有効な研究が展開されている(2.7 章,横山による説明に関する議論を参照のこと)。
BL6U は,繁政が管理するビームラインであり,最新鋭で競争力が高い。偏角可変型不等刻線平面回折格子(PGM)
分光器は,非常に高い分解能で高強度の軟X線を供給する。現在,アンジュレータの最小ギャップ値が設計値の 10
mm に及ばない 13 mm に制限されている。このため,カバーできない光エネルギー領域が生じているので,その原因
を同定し,もし可能であれば改善すべきである。BL6U の以下の二つの接続装置は,国際競争力がある。気相のオージェ
点検評価と課題 303
のになっている。MBS 社製 A-1 電子分析器もまた極めて国際競争力があり,気相の二次元電子分光法に利用されて
いる。傑出した国際共同研究者ら(Lablanquie, Simon, Piancastelli)が利用していることからその競争力がわかる。
UVSOR Activity Report 2011 に沿って繁政から示された気相実験の例は,放射光を利用した分子動力学や光物理学の
優れた例になっている。私が特に賞賛するのは,CF4 分子の炭素 1s 励起に伴う超高速解離に関する研究(53 頁),及
び硫黄 2p 電子を励起した OCS 分子からのオージェ電子に観測されるドップラー分裂に関する研究(56 頁)である。
BL6U は,UVSOR を利用した分子科学として目立つ成果をあげており,十分に支援を続けるべきである。また,国
際的な分野コミュニティーから適切な共同研究者や単独で研究可能な研究者を見つけ出すことによって,UVSOR 施
現在,繁政とグループメンバーは,先端的な分子光物理研究のために SACLA のX線自由電子レーザーを使っている。
これは,UVSOR のためにも非常に好ましい展開である。すなわち,SACLA での研究を補完するために UVSOR を利
2.4. 固体のX線吸収,X線発光,及び角度分解光電子分光(BL3U,BL6U:山根宏之,IMS 小杉グループ助教)
BL3U は,軟X線吸収(XAS),軟X線発光(XES),共鳴X線散乱(RIXS)の世界ランクの設備であり,所内外の
研究者によって他施設では見られないような研究を可能にしている。有機 LED,有機エレクトロニクス,有機太陽電
池に関連した有機導体や有機半導体の XAS による研究は印象的であった。特に,蛍光収量 XAS(FY-NEXAFS)を用
いた電圧印加した有機物質の電子構造の operando 観測の例(PRL 107 (2011) 147401)は興味深い。この XAS 研究は
私の知る限り世界初のデバイス材料の operando 観測例である。有機伝導体や有機半導体の電気伝導には普通,π 状
態が関与していると信じられているが,驚いたことに本研究は,電気伝導に直接は関与しないと考えられている σ
BL3U の軟X線発光(XES)分光器は他の放射光施設にはないような性能を示しており,特に,140 eV 以下の低エ
ネルギー領域で 100 meV というエネルギー分解能を達成しており,十分な世界的競争力を有している。また,新規透
ることで,DNA のモデル分子(poly(G-C),poly(A-T))や窒素ドープグラフェン(J. Phys. Chem. C 116 (2012) 16251)
などの興味深い系の研究に利用されている。XES 分光器用の新しい高性能透過型回折格子が手に入れば,エネルギー
分解能や検出効率のさらなる向上が期待できる。XES 及び RIXS を応用した有機デバイスの動作環境下の operando 観
BL6U における有機固体・薄膜の角度分解光電子分光(ARPES)研究では傑出した計画が山根によって報告された。
実験装置は世界的に見てトップクラスであり,5 meV 以下のエネルギー分解能(励起光,電子),13 K までの冷却能,
技術開発は装置開発室の優秀さの賜であり,これは UVSOR 施設と IMS にとって正に財産と言える。有機薄膜調製や
他の試料調製を可能とする試料準備槽も注目に値する。BL6U では強力な国際参加がある。カーボンナノチューブと
ワイドギャップ半導体界面でのバンドアライメント(丸山),Pt の1次元ナノワイヤー中のスピン−軌道(ラシュバ)
分裂(Yeom),DNA ワトソン−クリック混合膜中におけるナノレベルでの相分離(Friedlein),金属フタロシアニン
304 点検評価と課題
射光の照射スポットを走査することで試料損傷の影響を回避している。BL6U の ARPES 装置は有機固体・薄膜の装
BL6U の性能の更なる強化・改善に向けて,先にも述べた試料損傷の影響を少なくするための検出効率の向上(例
えば,VG シエンタ社製 D80 アナライザーへの更新),試料測定槽の更新,ビームライン光学系の炭素汚染除去用の
酸素ガス導入システムの導入などの提案が山根からあった。出来る限り BL6U で新しい分子科学研究が行えるように,
UVSOR 施設あるいは研究所として,これらの提案を真摯に検討すべきである。
2.5 走査型透過軟X線顕微鏡(BL4U:大東琢治,UVSOR 施設助教)
BL4U は,STXM 専用の新しい軟X線アンジュレータビームラインである。STXM は基礎科学,応用科学の両面で
利用可能なかなり新しい分光手法である。UVSOR 施設での研究計画は非常に野心的である。装置開発や技術開発(ク
ライオ顕微分光,クライオトモグラフィー,タイコグラフィー)には相当の努力が必要であり,まずは STXM の基本
性能が安定に得られるようにしたあとで取り組むべきである。UVSOR 施設における STXM プロジェクトは他の
STXM 装置と比較して相当優位な点がある。それは研究所内で試料作成ができることである(ウルトラミクロトーム,
FIB 処理,エンコーダーと顕微操作ができる最高レベルの光学顕微鏡など)。BL4U と STXM 装置は国のナノテクノ
ロジー・プラットフォーム事業の一環で利用される。これは極めて妥当であり,その結果,STXM を補完する電子顕
2.6 固体科学(BL1B,BL5U,BL6B,BL7U:木村真一,UVSOR 施設准教授)
BL7U と BL5U は,どちらも表面や固体の角度分解光電子分光(ARPES)に使われているものであり,申請された
シフト数に対して配分されたシフト数の割合と高いレベルの雑誌に出版された論文数から判断して,UVSOR で1番
目・2番目に人気のあるビームラインである。BL7U は,低エネルギー光を用いた凝縮系の電子構造研究の装置とし
光エネルギー(100 eV 以上)のビームラインが使われる。BL7U では極めて低い電子エネルギーを使うことでバルク
敏感を実現している。2 meV のエネルギー分解能(励起光,電子)は,世界でほんの少しのビームラインだけで達成
している。APPLE-II 型挿入光源によって,試料のすべての偏光性を観測できる。BL7U で得られた傑出した凝縮系の
研究である。7~9 eV の光エネルギーの範囲でサブミクロンのスポットサイズを実現するために現在開発中の従来型集
光技術による装置は,米国 ALS 放射光施設(Maestro ビームライン)や仏国 Soleil 放射光施設(Antares ビームライン)
のような高エネルギー光を使った nano-ARPES 装置を補完できる,世界的にもユニークな装置になるであろう。この
ような面内方向のヘテロ表面が解析できる装置の有効性を示す例として,k-(ET) 2 Cu[N(CN) 2 ]Br においてサブミクロ
ンスケールで起こると考えられている,新しい電子相分離系が取り上げられていた。いずれにしても,BL7U は,もっ
BL5U は,ちょっと古くて性能の低いビームラインであるが,その高い光エネルギー(200 eV まで)は BL7U をう
点検評価と課題 305
まく補完している。BL5U の性能を向上させるための改造計画が説明された。そこでは,BL7U の分解能 10000–50000
に対してたった 3000 の分解能である現有分光器の更新が含まれている。BL7U や 5U では有機物質についての利用研
BL6B は,赤外とテラヘルツ領域をカバーしており,偏向電磁石からの赤外放射を他とは比較にならないくらいに
大きく取り込むことが可能な木村独自のマジックミラー(ただし,集光性能はウィスコンシンの SRC 施設の IRENI
は放射光赤外分光や顕微分光を使った分子科学研究が広く行われているのと比較すると,BL6B では分子科学がほと
んどないに等しい。IMS では有機電子物質や生物科学の研究が行われていることを考えれば,BL6B の利用拡大可能
て BL6B を専有利用することに興味を持っていることを知った。「長期利用課題」のような新しいブログラム(木村
の金曜日のプレゼンの最後の説明)は,BL6B の赤外顕微鏡を使って分子科学研究を強化する絶好の機会であると思
われる。STXM と赤外顕微鏡を相補的に併用した,先導的研究も多くある。それを容易にするには,試料取付方法の
共通化や相互可換化,さらに基準点設定(BL4U の STXM 装置のために設置している光学顕微鏡のエンコードステー
BL1B は,振幅変調されたパルス列でレーザースライスされた新しいコヒーレントなテラヘルツ光やテラヘルツ・
2.7 磁性材料のX線吸収分光(XAS),X線磁気円二色性(XMCD)(BL4B:横山利彦,IMS グループ)
BL4B の超伝導磁石磁気分光システムは国際的に競争力のある設備である。世界の放射光施設に設置されている同
W(110) 表面上の島状並びに縞状 Fe,Cu(110)-(2×3)N 表面上の Co ナノロッド,Cu(001) 表面上の γ’-FeN,Si 3 N 4 /
Si(111)-(8×8) 上の Fe,Si(111) 表面上のバナジルフタロシアニン VOPc の5件である。最後の 1 件のみが分子に関する
研究例である。この研究では,X線吸収端近傍微細構造(NEXAFS)の偏光依存性と V 2p のX線磁気円二色性(XMCD)
測定から,構造と磁性を評価している。単層と多層 VOPc では電子状態や化学結合に大きな違いがあるが,V 2p
XMCD は似通っており V 3d 磁性は単層でも保持されているという結果であった。紹介されたすべての研究例で,極
のの,ビームタイムに制約の少ない UVSOR 施設では,丁寧な in situ 測定が必須の試料について十分に時間をかけて
306 点検評価と課題
2.8 有機固体の光電子放出(BL8B:解良聡,千葉大准教授)
BL8B は,有機固体の角度分解光電子分光(ARPES)及び紫外光電子分光法専用の公開ビームラインである。ヒア
導機構,ルブレン結晶のバンド分散測定などが報告された。BL8B は UVSOR における最も古いビームラインである。
真空紫外領域における ARUPS による有機固体の波数空間軌道マップ測定を可能とするためには,より高い性能が必
要であり,装置の改良計画として,BL8B から BL2B への移設,最新の二次元検出器を有する分析器への更新が提案
された。このような方向性については,最近行われた ICESS12 国際会議において多くの関連成果が発表されており,
2.9a 真空紫外領域の光物性(BL3B,BL7B:木村真一,UVSOR 施設准教授)
BL3B と BL7B は可視から真空紫外領域の光物性研究(反射,吸収,発光)に使われている。BL7B は古いビーム
ラインであり,最近エリプソメトリー測定に集中するために再配置された。BL3B は,最近 BL1B から移動され,高
いフラックス(以前の BL1B に比べて)と K-B ミラー系を用いることによる小さなスポットサイズを持つ HOTRLU
高い生産性がある(BL3B と BL7B は過去5年間に UVSOR 関連の発表論文の 20% 以上を生み出している)。
2.9b 生物学的分子の真空紫外分光(BL3B,BL7B:中川和道,神戸大学教授)
中川教授は個々のアミノ酸と DNA 塩基の透過率を詳細に測定し吸収断面積を絶対値で決定する研究について報告
した。最終的な信頼性は 5–10% で,総和則による補正を一部行っている。本研究の動機に紫外バイオセンサーや白
3. UVSOR における研究と将来の方向性に関する一般的評価
3a. 国際的競争力
BL3U,BL6U,BL3B を挙げる。
3b. 使命としての分子科学への適合性
学に直結する分野である。分子科学に非常に適合している気相分光研究は UVSOR 施設でも長い伝統がある。しかし,
点検評価と課題 307
3c. 所内研究者の役割と将来の方向性
研究の方向性,装置開発,ビームタイムの多くを所内研究者が決定しているところが,UVSOR の重要な鍵である。
これは他の放射光施設とは対極にある。他施設で支配的なのは外部研究者の研究と興味である。UVSOR の本当の強
ダー,そのチームに引き込む所外研究者,そして国際共同研究者のレベルに強く依存する。IMS は運良く何人かの非
常に能力の高い研究者を抱えている。他施設に比較して,UVSOR スタッフのサイズは非常に小さいにもかかわらず,
その成果は質,広がり,量の点で際だっている。しかし,少なくとも教授・准教授を1名,IMS あるいは UVSOR に
を探すべきではあるが,もし同等の優れた候補がいた場合には,ナノサイエンス分野の研究者が UVSOR の既存の装
Adam P. Hitchcock, FRSC
カナダ McMaster 大学
308 点検評価と課題