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Trapped exciton states in the alkali halides
xii
ABSTRACTS OF PAPERS TO APPEAR
c h r o m i u m - n i c k e l alloys p r o d u c e s the s c a l e c o m p o s e d of the solid solution of NiS in Cr~Sa. Growth of the r e a c t i o n product in the both s y s t e m s p r o c e e d s e x c l u s i v e l y due to the outward diffusion of the m e t a l , the r a t e of f o r m a t i o n of the solid solution being lower than that of p u r e c h r o m i u m sulphide. It is concluded that c h r o m i u m sulphide exhibits defects in the cation sublattice in f o r m of cation v a c a n c i e s and e l e c t r o n holes.
IN J. PHYS. C H E M . SOLIDS
The u l t r a v i o l e t a b s o r p t i o n s p e c t r u m of single c r y s t a l s of n o m i n a l l y p u r e Sc~O~ was m e a s u r e d at r o o m t e m p e r a t u r e and at liquid nit r o g e n t e m p e r a t u r e . The r e s u l t s a r e c o m p a r e d with the p r o b a b l e e n e r g y l e v e l s t r u c t u r e of the s y s t e m . An e s t i m a t e of the expected position of the a b s o r p t i o n t h r e s h o l d b a s e d on a s i m p l e c h a r g e t r a n s f e r m o d e l gives r e a s o n a b l e a g r e e m e n t with the o b s e r v e d a b s o r p t i o n edge. (Received 8 N o v e m b e r 1965) (Revised 4 J a n u a r y 1966)
(Received 28 S e p t e m b e r 1965) 20. T H E O R E T I C A L DETERMINATION OF THE COHESIVE ENERGY, THE L A T T I C E P A R A M E T E R AND THE COMPRESSIBILITY OF L i F CRYSTAL. K. M a n s i k k a and F. B y s t r a n d (Quantum C h e m i s t r y Group f o r R e s e a r c h in Atomic, M o l e c u l a r and Solid-State T h e o r y , Uppsala U n i v e r s i t y , Uppsala, Sweden).
The c o h e s i v e e n e r g y , the lattice p a r a m e t e r , and the c o m p r e s s i b i l i t y of the s t a t i c L i F c r y s t a l have been d e t e r m i n e d in the H e i t l e r London s c h e m e by m e a n s of t h r e e different quantum m e c h a n i c a l a p p r o x i m a t i o n s . The f i r s t a p p r o x i m a t i o n c o r r e s p o n d s to the f r e e ion model. In the second a p p r o x i m a t i o n the r a d i a l d e f o r m a tion of F - - i o n due to the c r y s t a l field was taken into account by scaling the e x t e n s i v e 2 p - w a v e functions. In the t h i r d a p p r o x i m a t i o n , a l s o the d e f o r m a t i o n of Li + - i o n was t a k e n into account by coupling the above 2 p - s c a l i n g and the u n i f o r m o v e r - a l l scaling t o g e t h e r . The v a l u e s of the scaling f a c t o r s w e r e calculated a s a function of interionic d i s t a n c e by t r e a t i n g t h e m as v a r i a tioual p a r a m e t e r s . The r e s u l t s obtained f r o m different a p p r o x i m a t i o n s a g r e e well with the c o r r e s p o n d i n g e x p e r i m e n t a l data. However, c e r t a i n i m p r o v e m e n t s a r e gained when using the d e f o r m a t i o n m o d e l of the ions. The v i r l a l t h e o r e m , a n e c e s s a r y condition for an exact wave function, is s a t i s f i e d in the t h i r d a p p r o x i mation too. The values of the scaling p a r a m e t e r s indicate that in the c r y s t a l F - - i o n s a r e cont r a c t e d and Li ÷ - i o n s slightly extended a s c o m p a r e d to the f r e e ion s t a t e s . (Received 25 October 1965) (Revised 3 J a n u a r y 1966) 21. ABSORPTION EDGE SPECTRUM OF SCANDIUM OXIDE. H . H . Tippins ( A e r o s p a c e C o r p o r a t i o n , E1 Segundo, California).
Vol. 4, No. 2
22. T R A P P E D E x c r r o N
STATES IN THE A L K A L I HALIDES. G. Baldini and K. T e e g a r d e n (Institute of Optics, U n i v e r s i t y of R o c h e s t e r , R o c h e s t e r ,
N.Y.). The a b s o r p t i o n s p e c t r a of thin f i l m s of RbC1 containing 1 m o l % of RbI and KC1 containing 1 m o l % of KI m e a s u r e d at low t e m p e r a t u r e a r e p r e s e n t e d . T h e s e s p e c t r a show s t r u c t u r e which is analogus to the s t r u c t u r e s e e n in the exctton s p e c t r a of p u r e KI and RbI. Both the well known spin o r b i t doublet and lines c o r r e s p o n d i n g to effective m a s s s t a t e s of the bound h o l e - e l e c t r o n p a i r a p p e a r . An a t t e m p t is m a d e to c a l c u l a t e the effective m a s s of an e l e c t r o n in the host c r y s t a l f r o m the a b s o r p t i o n s p e c t r a . A value o f . 66 is obtained f o r the c a s e of RbCI:RbI. (Received 18 N o v e m b e r 1965) 23. COMPRESSIBILITY OF SOLIDS AND T A I T ' S LAW II ATOMIC RADH OF THE A L K A L I METALS. R o b e r t Ginell and T h o m a s J. Quigley (Dep a r t m e n t of C h e m i s t r y , Brooklyn College of The City U n i v e r s i t y of New York).
The p r e v i o u s l y u n d e t e r m i n e d constant A is evaluated u n a m b i g u o u s l y and a g e n e r a l method of p e r f o r m i n g such evaluations is given. The a t o m i c r a d i i of the alkali m e t a l s in the solid s t a t e a r e c a l c u l a t e d f r o m the c o m p r e s s i b i l i t y p a r a m e t e r s of the m e t a l s through an evaluation of the excluded v o l u m e , beth, B. The v a l u e s obtained a r e in excellent a g r e e m e n t with both the Slater and B r a g g values. It is shown that on c o m p r e s s i o n , the v o l u m e d e c r e a s e is due to the d i s a p p e a r a n c e of the defect v o l u m e and the int e r n a l v o l u m e in the a g g r e g a t e s and that up to about 1 0 0 , 0 0 0 k g / c m 2 for lithium, sodium, pot a s s i u m and r u b i d i u m and to about 23,000 k g / c m 2 for c e s i u m the r a d i i of the a l k a l i m e t a l s p r o b a b l y
ABSTRACTS OF PAPERS TO APPEAR
c h r o m i u m - n i c k e l alloys p r o d u c e s the s c a l e c o m p o s e d of the solid solution of NiS in Cr~Sa. Growth of the r e a c t i o n product in the both s y s t e m s p r o c e e d s e x c l u s i v e l y due to the outward diffusion of the m e t a l , the r a t e of f o r m a t i o n of the solid solution being lower than that of p u r e c h r o m i u m sulphide. It is concluded that c h r o m i u m sulphide exhibits defects in the cation sublattice in f o r m of cation v a c a n c i e s and e l e c t r o n holes.
IN J. PHYS. C H E M . SOLIDS
The u l t r a v i o l e t a b s o r p t i o n s p e c t r u m of single c r y s t a l s of n o m i n a l l y p u r e Sc~O~ was m e a s u r e d at r o o m t e m p e r a t u r e and at liquid nit r o g e n t e m p e r a t u r e . The r e s u l t s a r e c o m p a r e d with the p r o b a b l e e n e r g y l e v e l s t r u c t u r e of the s y s t e m . An e s t i m a t e of the expected position of the a b s o r p t i o n t h r e s h o l d b a s e d on a s i m p l e c h a r g e t r a n s f e r m o d e l gives r e a s o n a b l e a g r e e m e n t with the o b s e r v e d a b s o r p t i o n edge. (Received 8 N o v e m b e r 1965) (Revised 4 J a n u a r y 1966)
(Received 28 S e p t e m b e r 1965) 20. T H E O R E T I C A L DETERMINATION OF THE COHESIVE ENERGY, THE L A T T I C E P A R A M E T E R AND THE COMPRESSIBILITY OF L i F CRYSTAL. K. M a n s i k k a and F. B y s t r a n d (Quantum C h e m i s t r y Group f o r R e s e a r c h in Atomic, M o l e c u l a r and Solid-State T h e o r y , Uppsala U n i v e r s i t y , Uppsala, Sweden).
The c o h e s i v e e n e r g y , the lattice p a r a m e t e r , and the c o m p r e s s i b i l i t y of the s t a t i c L i F c r y s t a l have been d e t e r m i n e d in the H e i t l e r London s c h e m e by m e a n s of t h r e e different quantum m e c h a n i c a l a p p r o x i m a t i o n s . The f i r s t a p p r o x i m a t i o n c o r r e s p o n d s to the f r e e ion model. In the second a p p r o x i m a t i o n the r a d i a l d e f o r m a tion of F - - i o n due to the c r y s t a l field was taken into account by scaling the e x t e n s i v e 2 p - w a v e functions. In the t h i r d a p p r o x i m a t i o n , a l s o the d e f o r m a t i o n of Li + - i o n was t a k e n into account by coupling the above 2 p - s c a l i n g and the u n i f o r m o v e r - a l l scaling t o g e t h e r . The v a l u e s of the scaling f a c t o r s w e r e calculated a s a function of interionic d i s t a n c e by t r e a t i n g t h e m as v a r i a tioual p a r a m e t e r s . The r e s u l t s obtained f r o m different a p p r o x i m a t i o n s a g r e e well with the c o r r e s p o n d i n g e x p e r i m e n t a l data. However, c e r t a i n i m p r o v e m e n t s a r e gained when using the d e f o r m a t i o n m o d e l of the ions. The v i r l a l t h e o r e m , a n e c e s s a r y condition for an exact wave function, is s a t i s f i e d in the t h i r d a p p r o x i mation too. The values of the scaling p a r a m e t e r s indicate that in the c r y s t a l F - - i o n s a r e cont r a c t e d and Li ÷ - i o n s slightly extended a s c o m p a r e d to the f r e e ion s t a t e s . (Received 25 October 1965) (Revised 3 J a n u a r y 1966) 21. ABSORPTION EDGE SPECTRUM OF SCANDIUM OXIDE. H . H . Tippins ( A e r o s p a c e C o r p o r a t i o n , E1 Segundo, California).
Vol. 4, No. 2
22. T R A P P E D E x c r r o N
STATES IN THE A L K A L I HALIDES. G. Baldini and K. T e e g a r d e n (Institute of Optics, U n i v e r s i t y of R o c h e s t e r , R o c h e s t e r ,
N.Y.). The a b s o r p t i o n s p e c t r a of thin f i l m s of RbC1 containing 1 m o l % of RbI and KC1 containing 1 m o l % of KI m e a s u r e d at low t e m p e r a t u r e a r e p r e s e n t e d . T h e s e s p e c t r a show s t r u c t u r e which is analogus to the s t r u c t u r e s e e n in the exctton s p e c t r a of p u r e KI and RbI. Both the well known spin o r b i t doublet and lines c o r r e s p o n d i n g to effective m a s s s t a t e s of the bound h o l e - e l e c t r o n p a i r a p p e a r . An a t t e m p t is m a d e to c a l c u l a t e the effective m a s s of an e l e c t r o n in the host c r y s t a l f r o m the a b s o r p t i o n s p e c t r a . A value o f . 66 is obtained f o r the c a s e of RbCI:RbI. (Received 18 N o v e m b e r 1965) 23. COMPRESSIBILITY OF SOLIDS AND T A I T ' S LAW II ATOMIC RADH OF THE A L K A L I METALS. R o b e r t Ginell and T h o m a s J. Quigley (Dep a r t m e n t of C h e m i s t r y , Brooklyn College of The City U n i v e r s i t y of New York).
The p r e v i o u s l y u n d e t e r m i n e d constant A is evaluated u n a m b i g u o u s l y and a g e n e r a l method of p e r f o r m i n g such evaluations is given. The a t o m i c r a d i i of the alkali m e t a l s in the solid s t a t e a r e c a l c u l a t e d f r o m the c o m p r e s s i b i l i t y p a r a m e t e r s of the m e t a l s through an evaluation of the excluded v o l u m e , beth, B. The v a l u e s obtained a r e in excellent a g r e e m e n t with both the Slater and B r a g g values. It is shown that on c o m p r e s s i o n , the v o l u m e d e c r e a s e is due to the d i s a p p e a r a n c e of the defect v o l u m e and the int e r n a l v o l u m e in the a g g r e g a t e s and that up to about 1 0 0 , 0 0 0 k g / c m 2 for lithium, sodium, pot a s s i u m and r u b i d i u m and to about 23,000 k g / c m 2 for c e s i u m the r a d i i of the a l k a l i m e t a l s p r o b a b l y