Fig. 1. Optical layout of the monochromator at BL27SU. Synchrotron radiation sources and the soft X-ray mono chro mato rs have been impr oved sign ific antl y in the past few decades. Currently, it is possible to p r o m o t e a s p e c i f i c i n n e r - s h e l l e l e c t r o n t o a n y u n o c c u p i e d a t o m i c a n d m o l e c u l a r o r b i t a l w i t h a n e x c i t a t i o n p h o t o n b a n d p a s s s m a l l e r t h a n t h e na tu ra l wi dt h of th e in ne r- sh el l ex ci te d st at es . In t h i s c o n t e x t , t h e e x p e r i m e n t a l w i d t h o f t h e A u g e r lines is not determined by the natural width of the i n n e r - s h e l l e x c i t e d s t a t e s , b u t , i n g e n e r a l , b y t h e convolution of the excitation photon band pass and the band pass of the electron energy analysis. This li ne nar ro wi ng eff ec t, oft en cal le d th e Au ge r re so na nt R a m a n e f f e c t , h a s b e e n u s e d f o r s p e c t r o s c o p i c investigations of the Auger final states of rare gas atoms , as well as for inves tigat ions of the nucle ar HIGH-RESOLUTION RESONANT AUGER ELECTRON SPECTROSCOPY FOR INVESTIGATING NUCLEAR MOTION IN CORE-EXCITED MOLECULES MO M1 178.8 ° 178.8 ° S1 M21 M22 G S2 M3 42.7 m 2 m 12 m 12.5 m 175.4 ° 178 ° Spherical Mirrors Gratings Exit Slit Toroidal Mirror 7.5 m 1 m E n t r a n c e S l i t B e n d C y l i n d e r Mirror Cylinder Mirror Figure-8 Undulator m o t i o n d y n a m i c s o f t h e i n n e r - s h e l l e x c i t e d m o l e c u l e s . T h e i n n e r - s h e l l e x c i t e d m o l e c u l e t h u s c r e a t e d d e c a y s m o s t l y v i a t h e r e s o n a n t A u g e r e m i s s i o n , i n i t i a t i n g m o l e c u l a r d i s s o c i a t i o n . N u c l e a r m o t i o n , h o w e v e r , o c c u r s i n t h e c o r e - e x c i t e d s t a t e o n a timescale of tens of fs, which is the lifetime of the inn er- she ll exc ite d sta te, aff ect ing the dis soc iat ion after the Auger decay. The objective of this study is to es ta bl is h re so na nt Au ge r sp ec tr os co py as a d i r e c t p r o b e o f t h e n u c l e a r m o t i o n i n t h e c o r e - excited states. Experiments were performed at the soft X-ray p h o t o c h e m i s t r y e x p e r i m e n t a l s t a t i o n ( C - s t a t i o n ) i n s t a l l e d a t b e a m l i n e B L 2 7 S U [ 1 ] . T h i s e x p e r i m e n t a l s t a t i o n i s d e s i g n e d f o r t h e s t u d y o f photoionization and electronic relaxation dynamics Fig. 2. Total ion yield spectrum of Ne at K-edge. Ne K -edge 1s -1 n p Rydberg Ne + 3 4 5 6 0.2 0 0.4 0.6 0.8 1 1.2 Photon Energy ( eV ) 863 865 867 869 871 Total Ion Yield ( arb. units) of core-excited atoms and molecules, as well as the o b s e r v a t i o n o f i o n f r a g m e n t a t i o n p r o c e s s e s o f m o l e c u l e s b y u s i n g a h i g h r e s o l u t i o n m o n o c h r o m a t o r ( E / ∆ E > 1 0 0 0 0 ) . T h e m o n o c h r o m a t o r i s o f t h e H e t t r i c k t y p e , a n d i s e q u i p p e d w i t h v a r i e d l i n e s p a c i n g p l a n e g r a t i n g s a n d s p h e r i c a l f o c u s i n g mirrors [2] . Figure 1 shows the optical layout of the monochromator. Three gratings and two spherical mirrors cover the photon energy range from 0.2 to 3 k e V . B y m e a s u r i n g t h e p h o t o a b s o r p t i o n spectrum of rare gas atoms and N 2 in the K -shell e x c i t a t i o n r e g i o n , t h e r e s o l v i n g p o w e r ( E / ∆ E ) i s es ti ma te d te nt at iv el y. Fo r ex am pl e, Fi g. 2 sh ow s th e Ne ph ot oa bs or pt io n sp ec tr um in th e 1 s → n p Rydberg resonance excitation region. The 1 s → n p ( n = 3 - 6 ) t r a n s i t i o n s a r e c l e a r l y d i s c e r n e d i n t h e sp ec tr um . Co mp ar is on wi th ot he r hi gh -r es ol ut io n photoabsorption measurements leads an estimated resolving power (E/ ∆ E) of better than 10000. The details of the monochromator and the performance tests have been reported in recent articles [3-5] . I n t h e p a s t y e a r , w e h a v e i n s t a l l e d a h i g h - resolution electron energy spectroscopy apparatus ( GAMMADATA-SCIENTA SES 2002 with a tunable gas cell GC-50 ) onto the beamline as a part of the e n d s t a t i o n a n d i n i t i a t e d t h e s u b n a t u r a l - w i d t h r e s o n a n t A u g e r e l e c t r o n s p e c t r o s c o p y o f a t o m s a n d m o l e c u l e s [ 6 - 8 ] . T h e f i r s t r e s u l t o f t h i s investigation using the Ne 1 s → 3 p excitation is as f o l l o w s . F i g u r e 3 s h o w s t h e o b s e r v e d r e s o n a n t A u g e r e m i s s i o n l i n e s , w h o s e f i n a l s t a t e s a r e N e + 2 p - 2 ( 1 D 2 ) 3 p . T h e p h o t o n b a n d p a s s a n d t h e band pass for the electron energy analyzer are 60- 6 8 m e V a n d 1 3 m e V , r e s p e c t i v e l y , w h i l e t h e D o p p l e r w i d t h d u e t o t h e r m a l m o t i o n o f t h e N e a t o m s i s 7 9 m e V . T h e m e a s u r e d w i d t h o f 1 0 0 - 10 5 me V is th e co nv ol ut io n of th es e th re e wi dt hs and is much smal ler than the natu ral widt h of the Ne 1 s hole state (~ 250 meV ). At this resolution, w e d i s t i n g u i s h e d f o r t h e f i r s t t i m e t h r e e m u l t i p l e t components — 2 P, 2 D, and 2 F — and confirmed t h a t t h e m e a s u r e d v a l u e s o f t h e a n i s o t r o p y p a r a m e t e r β f o r t h e s e t h r e e a r e i n e x c e l l e n t agreement with the theoretical predictions [8] . Fig. 3. Part of the electron spectra of the resonant Auger transitions from the Ne 1s -1 3p state to the final Ne + 2p -2 ( 1 D 2 ) 3p — 2 D, 2 P and 2 F — states recorded at a p h o t o n e n e r g y o f 8 6 7 . 1 2 e V w i t h h o r i z o n t a l ( u p p e r ) a n d v e r t i c a l ( l o w e r ) polarizations. The electron spectrometer axis is in the horizontal direction. Yuske Tamenori a , Haruhito Ohashi a and Kiyoshi Ueda b (a) SPring-8 / JASRI (b) Tohoku University E-mail: tamenori @ spring8.or.jp References [1] I. Koyano et al. , J. Synchrotron Rad. 5 (1998) 545. [2] M. C. Het tri ck and S. Bow yer , App l. Opt . 22 (1983) 3921. [3] E. Ishiguro et al. , J. Electron Spectros. Relat. Phenom. 101-103 (1999) 979. 0.2 0.4 0.6 0.8 0 1 Intensity ( arb. units) Kinetic Energy ( eV ) 810.9 811.1 811.3 811.5 811.7 811.9 2 D 2 P 2 F 0.2 0.4 0.6 0.8 0 1 1.2 [ 4 ] H . O h a s h i . E . I s h i g u r o , Y . T a m e n o r i , H . O k u m u r a , A . H i r a y a , H . Y o s h i d a , Y . S e n b a , K . Okada, I. H. Suzuki, N. Saito, K. Ueda, T. Ibuki, S. N a g a o k a , I . K o y a n o a n d T . I s h i k a w a , N u c l . Instrum. Meth. (2001) - in press. [ 5 ] Y . T a m e n o r i , H . O h a s h i , E . I s h i g u r o , H . O k u m u r a , T . F u k u i , T . M i u r a , H . K i s h i m o t o , J . T a n a s e , N . K a m a c h i , K . E n d o a n d T . I s h i k a w a , Nucl. Instrum. Meth. (2001) - in press. [6] Y. Shimizu et al. , J. Phys. B 33 (2000) L685. [ 7 ] Y . M u r a m a t s u e t a l . , C h e m . P h y s . L e t t . 3 3 0 (2000) 91. [8] Y . S h i m i z u , H . O h a s h i , Y . T a m e n o r i , Y . M u r a m a t s u , H . Y o s h i d a , K . O k a d a , N . S a i t o , H . T a n a k a , I . K o y a n o , S. Shin and K. Ueda, J. Electron Spectros. Relat. Phenom. (2001) - in press.
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