Kastler, Alfred

Leuchs, G.

Riedle, Eberhard

Smith, S. J.

Walther, H.

English

Universität München: Elektronischen Publikationen

Europhysics Study Conference 
on Multiphoton Processes 
Benodet June 18-22 1979 
INVITED PAPERS 
Ν, DELONE (P.N. Lebedev Physical I n s t i t u t e , Moscow, U.S.S.R.) 
Multiphoton Ionization of atoms. 
L. ARMSTRONG (Johns Hopkins University, Baltimore, U.S.A.) 
Temporal behavior in resonant multiphoton i o n i z a t i o n of atoms. 
P. KNIGHT (Royal Holloway College, University of London, England) 
Quantum beat interference effects in resonant multiphoton ionization. 
P. LAMBROPOULOS (University of Southern C a l i f o r n i a , Los Angeles, U.S.A.) 
Fi e l d s t a t i s t i c s and bandwidth e f f e c t s i n resonant multiphoton 
ionization of atoms. 
Ϊ. GONTIER (C.E.A. Saclay, France) 
Resonant multiphoton ionization of atoms. 
S. HARRIS and J.F. YOUNG (Stanford University»Stanford, USA) 
Laser induced i n e l a s t i c c o l l i s i o n and r a d i a t i v e energy t r a n s f e r from 
metastable s t a t e s . 
S. FENEUILLE (Laboratoire Aime Cotton, Orsay, France) 
Theory of r a d i a t i v e - c o l l i s i o n a l reactions i n the two-level 
approximation. 
A. LAU (Exxon research and engineering Co, Linden, USA) 
Laser-controlled unimolecular and bimolecular processes : F i e l d s 
dependent rate constants. 
S. ANISIMOV (Landau I n s t i t u t e , Moscow, USSR) 
Laser induced multiphoton photoelectron emission from metals. 
N. BLOEMBERGEN (Harvard University, Cambridge, USA) 
A survey of multiphoton excitation processes. 
Μ. VAU DER WIEL (F.O.M. I n s t i t u t e , Amsterdam, The Netherlands) 
Multiphoton ionization of molecules. 
Y. LEE (University of C a l i f o r n i a , Berkeley, USA) 
Infrared multiphoton excitation and dissociation of molecules. 
R. HOCHSTRASSER (University of Pennsylvania, Philadelphia, USA) 
Two-photon spectroscopy of molecules. 
N.V. KARLOV, A.M. PR0KH0R0V (P.N. Lebedev Physical I n s t i t u t e , Moscow, USSR) 
Multiphoton processes in laser-induced chemical reactions. 
K.L, KOMPA. W. FUB, K. HOHLA, D. PROCH, J.REILLY, S.D. ROCKWOOD, Η. SCHRODER 
(Max-Planck I n s t i t u t e , Garching, Germany) 
Multiphoton processes and laser-induced chemical changes. 
M. FEDORQV (P.N. Lebedev Physical I n s t i t u t e , Moscow, USSR) 
Multiphoton stimulated Bremsstrahlung. 
S. GELTMAN (JILA, Boulder, USA) 
Multiphoton free-free transitions and ejected electron energy 
distribu t i o n s . 
G.LEUCHS, E. RIEDLE, S.J. SMITH, H. WALTHER 
(Universität München, Garching, All.Federale) 
Angular di s t r i b u t i o n of photoelectrons in three photon ionization 
of sodium. 
- 53 -
ANGULAR DISTRIBUTION OF PHOTOELECTRONS IN THREE PHOTON 
IONIZATION OF SODIUM 
G. L e u c h s , E. R i e d l e , S.J. Smith**", H. W a i t h e r * * 
S e k t i o n P h y s i k d e r U n i v e r s i t ä t München 
8046 G a r c h i n g , F e d e r a l R e p u b l i c o f Germany 
The a n g u l a r d i s t r i b u t i o n o f p h o t o e l e c t r o n s p r o d u c e d by m u l t i -
p h o t o n i o n i z a t i o n o f atoms i s a s e n s i t i v e t e s t f o r t h e 
i o n i z a t i o n p r o c e s s s i n c e t h e d i s t r i b u t i o n i s d e t e r m i n e d by t h e 
i n t e r m e d i a t e s t a t e s . I n t h i s p a p e r we r e p o r t m e a s u r e m e n t s o f t h e 
a n g u l a r d i s t r i b u t i o n w h i c h have been o b t a i n e d f o r r e s o n a n t 
t h r e e - p h o t o n i o n i z a t i o n . The r e s u l t s a l s o d e m o n s t r a t e t h a t t h e 
a n g u l a r d i s t r i b u t i o n can be changed by m i x i n g t h e i n t e r m e d i a t e 
s t a t e s by m i c r o w a v e t r a n s i t i o n s . T h i s can be us e d f o r o p t i c a l 
m i c r o w a v e e x p e r i m e n t s t o d e t e r m i n e t h e e n e r g y s p l i t t i n g 
o f R y d b e r g s t a t e s . 
I n t h e e x p e r i m e n t two n i t r o g e n l a s e r pumped dye l a s e r s were 
used t o e x c i t e t h e atoms o f a s o d i u m a t o m i c beam. The s o d i u m 
atoms were i o n i z e d i n t h e r e s o n a n t t h r e e - p h o t o n p r o c e s s 
2 2 2 2 ^ 
3 s 1 / 2 " > " 3 P l / 2 * 3 P3/2** Π D ^ l 1 » ^ · T h e e l e c t r o n s e m i t t e d 
i n t h e p l a n e p e r p e n d i c u l a r t o t h e d i r e c t i o n o f t h e l a s e r beams 
were d e t e c t e d w i t h an a n g u l a r r e s o l u t i o n o f 0.35 r a d . The a n g u l a r 
d i s t r i b u t i o n was p r o b e d by r o t a t i n g t h e d i r e c t i o n o f t h e l i n e a r 
p o l a r i z a t i o n o f t h e l a s e r l i g h t . 
I n t h e case o f s i n g l e - p h o t o n i o n i z a t i o n o f atoms w i t h an e q u a l 
p o p u l a t i o n o f t h e m - s u b l e v e l s t h e p h o t o e l e c t r o n a n g u l a r 
d i s t r i b u t i o n can be d e s c r i b e d by t h e g e n e r a l f o r m u l a 
1 ( 9 ) = 1 + 8 P 2 ( c o s 0 ) 
9 i s t h e a n g l e b e t w e e n t h e d i r e c t i o n o f e m i s s i o n o f t h e p h o t o -
e l e c t r o n and t h e l a s e r p o l a r i z a t i o n . 8 i s t h e a n i s o t r o p y p a r a ­
m e t e r and Ρ t h e s e c o n d L e g e n d r e p o l y n o m i a l . I n t h e case where 
- 54 -
m - s u b l e v e l s a r e s e l e c t i v e l y p o p u l a t e d i n a η-photon i o n i z a t i o n 
2 
p r o c e s s , h i g h e r powers o f cos θ have t o he i n c l u d e d : 
I (θ) = J~ a c o s 2 v 9 . η L — r ν v= 0 
Thus, f o r a r e s o n a n t m u l t i - p h o t o n i o n i z a t i o n p r o c e s s s h a r p 
maxima appear i n t h e a n g u l a r d i s t r i b u t i o n o f p h o t o e l e c t r o n s 
w h i c h c r i t i c a l l y depend on t h e quantum numbers o f t h e i n t e r ­
m e d i a t e s t a t e s / l / . E x p e r i m e n t s on s o d i u m d e m o n s t r a t i n g t h i s 
b e h a v i o u r a r e r e p o r t e d . 
F i s . : The a n e u l a r d i s t r i b u t i o n o f o h o t o -
e l e c t r o n s o r o d u c e d by r e s o n a n t 
2, 
^1/2 
i s shown i n a 
t h r e e - p h o t o n i o n i z a t i o n 3 S 
3/2 - Λ 
o o l a r d i a g r a m 
3 2P l , k > 
The s o l i d l i n e was 
o b t a i n e d i n a l e a s t s a u a r e s f i t o f 
t h e t h e o r e t i c a l r u n c t i o n I f f ( θ ) b t o 
t h e e x p e r i m e n t a l d a t a , g i v i n g 
2 M-I c ( 9 ) = 0.03+0.32cos 9-cos 9+0.87cos ο 
The a r r o w i n d i c a t e s t h e d i r e c t i o n 
o f l a s e r p o l a r i z a t i o n . 
+ + 
On s a b b a t i c a l l e a v e f r o m J I L A , B o u l d e r , C o l o r a d o 
a l s o P r o j e k t g r u p p e f u r L a s e r f o r s c h u n g d e r 
M a x - P l a n c k - G e s e l l s c h a f t z u r F o r d e r u n g d e r W i s s e n s c h a f t e n e 
8046 G a r c h i n g , F e d e r a l R e p u b l i c o f Germany 
/!/ P. L a m b r o p o u l o s , p r i v a t e c o m m u n i c a t i o n 


Angular Distribution of Photoelectrons in Three Photon Ionisation of Sodium

Open Access LMU

Europhysics Study Conference on Multiphoton Processes Benodet June 18-22 1979 INVITED PAPERS Ν, DELONE (P.N. Lebedev Physical I n s t i t u t e , Moscow, U.S.S.R.) Multiphoton Ionization of atoms. L. ARMSTRONG (Johns Hopkins University, Baltimore, U.S.A.) Temporal behavior in resonant multiphoton i o n i z a t i o n of atoms. P. KNIGHT (Royal Holloway College, University of London, England) Quantum beat interference effects in resonant multiphoton ionization. P. LAMBROPOULOS (University of Southern C a l i f o r n i a , Los Angeles, U.S.A.) Fi e l d s t a t i s t i c s and bandwidth e f f e c t s i n resonant multiphoton ionization of atoms. Ϊ. GONTIER (C.E.A. Saclay, France) Resonant multiphoton ionization of atoms. S. HARRIS and J.F. YOUNG (Stanford University»Stanford, USA) Laser induced i n e l a s t i c c o l l i s i o n and r a d i a t i v e energy t r a n s f e r from metastable s t a t e s . S. FENEUILLE (Laboratoire Aime Cotton, Orsay, France) Theory of r a d i a t i v e - c o l l i s i o n a l reactions i n the two-level approximation. A. LAU (Exxon research and engineering Co, Linden, USA) Laser-controlled unimolecular and bimolecular processes : F i e l d s dependent rate constants. S. ANISIMOV (Landau I n s t i t u t e , Moscow, USSR) Laser induced multiphoton photoelectron emission from metals. N. BLOEMBERGEN (Harvard University, Cambridge, USA) A survey of multiphoton excitation processes. Μ. VAU DER WIEL (F.O.M. I n s t i t u t e , Amsterdam, The Netherlands) Multiphoton ionization of molecules. Y. LEE (University of C a l i f o r n i a , Berkeley, USA) Infrared multiphoton excitation and dissociation of molecules. R. HOCHSTRASSER (University of Pennsylvania, Philadelphia, USA) Two-photon spectroscopy of molecules. N.V. KARLOV, A.M. PR0KH0R0V (P.N. Lebedev Physical I n s t i t u t e , Moscow, USSR) Multiphoton processes in laser-induced chemical reactions. K.L, KOMPA. W. FUB, K. HOHLA, D. PROCH, J.REILLY, S.D. ROCKWOOD, Η. SCHRODER (Max-Planck I n s t i t u t e , Garching, Germany) Multiphoton processes and laser-induced chemical changes. M. FEDORQV (P.N. Lebedev Physical I n s t i t u t e , Moscow, USSR) Multiphoton stimulated Bremsstrahlung. S. GELTMAN (JILA, Boulder, USA) Multiphoton free-free transitions and ejected electron energy distribu t i o n s . G.LEUCHS, E. RIEDLE, S.J. SMITH, H. WALTHER (Universität München, Garching, All.Federale) Angular di s t r i b u t i o n of photoelectrons in three photon ionization of sodium. - 53 -ANGULAR DISTRIBUTION OF PHOTOELECTRONS IN THREE PHOTON IONIZATION OF SODIUM G. L e u c h s , E. R i e d l e , S.J. Smith**", H. W a i t h e r * * S e k t i o n P h y s i k d e r U n i v e r s i t ä t München 8046 G a r c h i n g , F e d e r a l R e p u b l i c o f Germany The a n g u l a r d i s t r i b u t i o n o f p h o t o e l e c t r o n s p r o d u c e d by m u l t i -p h o t o n i o n i z a t i o n o f atoms i s a s e n s i t i v e t e s t f o r t h e i o n i z a t i o n p r o c e s s s i n c e t h e d i s t r i b u t i o n i s d e t e r m i n e d by t h e i n t e r m e d i a t e s t a t e s . I n t h i s p a p e r we r e p o r t m e a s u r e m e n t s o f t h e a n g u l a r d i s t r i b u t i o n w h i c h have been o b t a i n e d f o r r e s o n a n t t h r e e - p h o t o n i o n i z a t i o n . The r e s u l t s a l s o d e m o n s t r a t e t h a t t h e a n g u l a r d i s t r i b u t i o n can be changed by m i x i n g t h e i n t e r m e d i a t e s t a t e s by m i c r o w a v e t r a n s i t i o n s . T h i s can be us e d f o r o p t i c a l m i c r o w a v e e x p e r i m e n t s t o d e t e r m i n e t h e e n e r g y s p l i t t i n g o f R y d b e r g s t a t e s . I n t h e e x p e r i m e n t two n i t r o g e n l a s e r pumped dye l a s e r s were used t o e x c i t e t h e atoms o f a s o d i u m a t o m i c beam. The s o d i u m atoms were i o n i z e d i n t h e r e s o n a n t t h r e e - p h o t o n p r o c e s s 2 2 2 2 ^ 3 s 1 / 2 " > " 3 P l / 2 * 3 P3/2** Π D ^ l 1 » ^ · T h e e l e c t r o n s e m i t t e d i n t h e p l a n e p e r p e n d i c u l a r t o t h e d i r e c t i o n o f t h e l a s e r beams were d e t e c t e d w i t h an a n g u l a r r e s o l u t i o n o f 0.35 r a d . The a n g u l a r d i s t r i b u t i o n was p r o b e d by r o t a t i n g t h e d i r e c t i o n o f t h e l i n e a r p o l a r i z a t i o n o f t h e l a s e r l i g h t . I n t h e case o f s i n g l e - p h o t o n i o n i z a t i o n o f atoms w i t h an e q u a l p o p u l a t i o n o f t h e m - s u b l e v e l s t h e p h o t o e l e c t r o n a n g u l a r d i s t r i b u t i o n can be d e s c r i b e d by t h e g e n e r a l f o r m u l a 1 ( 9 ) = 1 + 8 P 2 ( c o s 0 ) 9 i s t h e a n g l e b e t w e e n t h e d i r e c t i o n o f e m i s s i o n o f t h e p h o t o -e l e c t r o n and t h e l a s e r p o l a r i z a t i o n . 8 i s t h e a n i s o t r o p y p a r a ­m e t e r and Ρ t h e s e c o n d L e g e n d r e p o l y n o m i a l . I n t h e case where - 54 -m - s u b l e v e l s a r e s e l e c t i v e l y p o p u l a t e d i n a η-photon i o n i z a t i o n 2 p r o c e s s , h i g h e r powers o f cos θ have t o he i n c l u d e d : I (θ) = J~ a c o s 2 v 9 . η L — r ν v= 0 Thus, f o r a r e s o n a n t m u l t i - p h o t o n i o n i z a t i o n p r o c e s s s h a r p maxima appear i n t h e a n g u l a r d i s t r i b u t i o n o f p h o t o e l e c t r o n s w h i c h c r i t i c a l l y depend on t h e quantum numbers o f t h e i n t e r ­m e d i a t e s t a t e s / l / . E x p e r i m e n t s on s o d i u m d e m o n s t r a t i n g t h i s b e h a v i o u r a r e r e p o r t e d . F i s . : The a n e u l a r d i s t r i b u t i o n o f o h o t o -e l e c t r o n s o r o d u c e d by r e s o n a n t 2, ^1/2 i s shown i n a t h r e e - p h o t o n i o n i z a t i o n 3 S 3/2 - Λ o o l a r d i a g r a m 3 2P l , k > The s o l i d l i n e was o b t a i n e d i n a l e a s t s a u a r e s f i t o f t h e t h e o r e t i c a l r u n c t i o n I f f ( θ ) b t o t h e e x p e r i m e n t a l d a t a , g i v i n g 2 M-I c ( 9 ) = 0.03+0.32cos 9-cos 9+0.87cos ο The a r r o w i n d i c a t e s t h e d i r e c t i o n o f l a s e r p o l a r i z a t i o n . + + On s a b b a t i c a l l e a v e f r o m J I L A , B o u l d e r , C o l o r a d o a l s o P r o j e k t g r u p p e f u r L a s e r f o r s c h u n g d e r M a x - P l a n c k - G e s e l l s c h a f t z u r F o r d e r u n g d e r W i s s e n s c h a f t e n e 8046 G a r c h i n g , F e d e r a l R e p u b l i c o f Germany /!/ P. L a m b r o p o u l o s , p r i v a t e c o m m u n i c a t i o n 

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Angular Distribution of Photoelectrons in Three Photon Ionisation of Sodium

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