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Note on the structure of the Ta I-spectrum
P h y s i c a X V I I , no 2
F e b r u a r i 1951
LETTER Note
on the
TO THE
Structure
EDITOR
of the
Ta
I-Spectrum
Our first r e p o r t on T a I 1) gives t h e s t a t e of t h e analysis in A u g u s t 1950. Since t h e n 9 e v e n levels and s o m e 70 odd levels h a v e been found. The n u m b e r of classified T a I-lines n o w exceeds 1100. A m o n g t h e new e v e n levels t h e r e is one g r o u n d level, viz. 5d36s 2 2Gu2; t h e o t h e r 8 c o n s t i t u t e t h e high e v e n t e r m 5d36s(SF) 7s6F and t h e corresponding levels 4F512' U~" This is the first case of series formation in t h e "Ca I - s p e c t r u m . T h a n k s to t h e i d e n t i f i c a t i o n of t h e high 6F t h e odd t e r m 5d 3 6s(SF) 6p6G c o u l d be established. I t has been necessary to change a n u m b e r of identifications. A m o n g t h e g r o u n d levels those labelled 5d46s 4D3/2,51~ " are now considered as 5d36s 2 2D312,5/2 on a c c o u n t of c o n f i g u r a t i o n calculations and c o m p a r i s o n w i t h a n a l o g o u s spectra: This explains w h y 5d46s 4D1/2,U~ could not be d e t e c t e d ; 4D is now e x p e c t e d a b o v e 15000 c m - - ' , b u t could not be localized t h u s far. T h e unidentified levels 153 (9/2), 159 (8/2) and 173 (7/2) are n o w labelled 5d 3 6s 2 2Hgl~, 2P312 and 2FU2 respectively. The g-factor of 5d 3 6s 2 2Dsl., is e x t r e m e l y irregular, b u t t h e g-sum f o r . J = 3/2 is p r a c t i c a l l y normal. This is t r u e also for J = 1/2, 5/2, 7/2 and 9/2 in spite of m a n y large d e p a r t u r e s f r o m t h e L a n d 6-values. So it seems t h a t the g r o u n d levels found h i t h e r t o c o n s t i t u t e a m o r e or less closed system. The h e a v y p e r t u r b a t i o n b e t w e e n 5d 4 6s 6D312 and 5d36s 2 2Dz!2 is v e r y r e m a r k a b l e . As regards t h e odd levels the c o n f i g u r a t i o n 5d46p has t u r n e d out to be m u c h h i g h e r t h a n was a s s u m e d previously. This was suggested b y the fact t h a t o u r c o n t i n u e d efforts to find t h e lowest s e x t e t 6F at the a n t i c i p a t e d position r e m a i n e d unsuccessful, and b y t h e d e t e c t i o n of a n e w set of odd s e x t e t levels a r o u n d 45000 c m - l which h a v e c o m b i n a t i o n s of o u t s t a n d i n g i n t e n s i t y w i t h 5d46s. Levels b e l o n g i n g to 5d4(SD) 6p 617, 6D and 6p could be recognized. These n e w identifications are fully s u b s t a n t i a t e d b y c o m p a r i n g t h e r e l a t i o n T a I - T a I I w i t h t h e c o r r e s p o n d i n g relations in V and Nb, and b y a p p l y i n g t h e irregular d o u b l e t law in t h e iso-electronic systems W I I ~) and T a I. The r e - i n t e r p r e t a t i o n entails new a s s i g n m e n t s for t h e 5d36s(Sp)6plevels, b u t those of t h e 5d36s(SF)6p-levels and t h e 5d26s 2 6 p - c o n f i g u r a t i o n are p r a c t i c a l l y unaffected. Full j u s t i f i c a t i o n will be given in a s u b s e q u e n t paper. The ionization energy can n o w be e v a l u a t e d from the position of 5d 3 6s(SF) 7s 4F, if one knows the decrease of t h e q u a n t u m defects in going f r o m 6s 2 to 6sTs. I n c o n n e c t i o n w i t h related spectra a reasonable v a l u e of --
167
--
168:
STRUCTURE OF TANTALUM I SPECTRUM
A s is O. 10. A p p l y i n g t h i s t o t h e 4F612- a n d 4 F , t~-series w e f i n d t h a t t h e l o w e s t l e v e l o f T a I, 5 d 3 6 s 2 4173h, h a s a v a l u e o f (62700 + 700) c m - 1 w i t h r e s p e c t
t o T a I I 5da6s s17 I. I f t h i s is t h e l o w e s t l e v e l o f T a I I , a s is a s s u m e d i n t h e p r e l i m i n a r y a n a l y s i s o f t h a t s p e c t r u m 3), t h e i o n i z a t i o n p o t e n t i a l o f T a I • b e c o m e s ( 7 . 7 7 + o . x o ) V o l t . T h e r e a r e i n d i c a t i o n s , h o w e v e r , t h a t in T a I I a l o w - l y i n g 3t7 is still m i s s i n g . Some conspicuous high odd sextet levels can be associated only with the 7p-electron. The ionization energy given above leads to a decrease of the quantum defect of 0.03-0.05 for the second members of these p-series ; this seems quite reasonable. All n e w e v e n l e v e l s a n d s o m e o f t h e o d d o n e s h a v e b e e n l i s t e d in t a b l e I TABLE I New Levels in Ta I .~ Value
J
'/2
Even g Identification 0.92 5dS6s ~ 2C-71,
41151.2~ 1/od --0.6~ 1.0C 41594.7S 1.37, 42501.58 5/2 1.4C 43982.5C 212 1.3~ 45636.84 47319.49 h
;/.
46981.86 512 47817.1C
I I Value 18504.78 19178.40 5da6s(SF)7s eF~h 22380.49] ,, eF*h 22681.701 ,, eF% 25008.921 ,, eF, h 26936.11 ,, eF~h 30361.29 ,, eFn/~ 44689.28 44806.74 ,, 'tFs/t 4s255.851 !46409.77 147799.94 148808.56 50660.46
Odd J t/2
g
0.87 '1~ 9/. 1.2E u] 2 1.3C ta/2 s/.
tl/z 1.35
s/2 1.81 9/2 1.36
5/,
1.67
'/2 1.44 0/~ 1.36 3Is 5/.,
Identification •5d'-6s2(SF)6p *Dt h 5dS6s(SF)6p aG612 ,, ,, ,, ,, ,, 5d4(6D)6p ,, ,, ,, ~t
5d36s(SFJ7p
,,
s~ h
eG~/s eGttls
6G~/t aF~t/s UDslt 6F, I, UD~h ~DTIs
aD,It eD31~ eDs/~
Received 21-2-51. P . F . A. KLINKENBERG. G. J. VAN DEN B~RG. J . C. VAN DEN BOSCH. Zeeman-Laboratorium aer Universiteit van Amsterdam
REFERENCES 1) K l i n k e n b e r g , P. F. A., V a n d e n B e r g , G. J. and V a n d e n B o s c h , J. C.. Physica 16 (1950), 861. 2) L a p o r t e , O. and M a c k , J. E., Phys. Rev. 63 (1943), 246. 3) K i e s s , C. C., H a r r i s o n , G. R. and H i t c h e o c k , W. J., J. Res. Bur. Stand. 44 (1950), 245.
F e b r u a r i 1951
LETTER Note
on the
TO THE
Structure
EDITOR
of the
Ta
I-Spectrum
Our first r e p o r t on T a I 1) gives t h e s t a t e of t h e analysis in A u g u s t 1950. Since t h e n 9 e v e n levels and s o m e 70 odd levels h a v e been found. The n u m b e r of classified T a I-lines n o w exceeds 1100. A m o n g t h e new e v e n levels t h e r e is one g r o u n d level, viz. 5d36s 2 2Gu2; t h e o t h e r 8 c o n s t i t u t e t h e high e v e n t e r m 5d36s(SF) 7s6F and t h e corresponding levels 4F512' U~" This is the first case of series formation in t h e "Ca I - s p e c t r u m . T h a n k s to t h e i d e n t i f i c a t i o n of t h e high 6F t h e odd t e r m 5d 3 6s(SF) 6p6G c o u l d be established. I t has been necessary to change a n u m b e r of identifications. A m o n g t h e g r o u n d levels those labelled 5d46s 4D3/2,51~ " are now considered as 5d36s 2 2D312,5/2 on a c c o u n t of c o n f i g u r a t i o n calculations and c o m p a r i s o n w i t h a n a l o g o u s spectra: This explains w h y 5d46s 4D1/2,U~ could not be d e t e c t e d ; 4D is now e x p e c t e d a b o v e 15000 c m - - ' , b u t could not be localized t h u s far. T h e unidentified levels 153 (9/2), 159 (8/2) and 173 (7/2) are n o w labelled 5d 3 6s 2 2Hgl~, 2P312 and 2FU2 respectively. The g-factor of 5d 3 6s 2 2Dsl., is e x t r e m e l y irregular, b u t t h e g-sum f o r . J = 3/2 is p r a c t i c a l l y normal. This is t r u e also for J = 1/2, 5/2, 7/2 and 9/2 in spite of m a n y large d e p a r t u r e s f r o m t h e L a n d 6-values. So it seems t h a t the g r o u n d levels found h i t h e r t o c o n s t i t u t e a m o r e or less closed system. The h e a v y p e r t u r b a t i o n b e t w e e n 5d 4 6s 6D312 and 5d36s 2 2Dz!2 is v e r y r e m a r k a b l e . As regards t h e odd levels the c o n f i g u r a t i o n 5d46p has t u r n e d out to be m u c h h i g h e r t h a n was a s s u m e d previously. This was suggested b y the fact t h a t o u r c o n t i n u e d efforts to find t h e lowest s e x t e t 6F at the a n t i c i p a t e d position r e m a i n e d unsuccessful, and b y t h e d e t e c t i o n of a n e w set of odd s e x t e t levels a r o u n d 45000 c m - l which h a v e c o m b i n a t i o n s of o u t s t a n d i n g i n t e n s i t y w i t h 5d46s. Levels b e l o n g i n g to 5d4(SD) 6p 617, 6D and 6p could be recognized. These n e w identifications are fully s u b s t a n t i a t e d b y c o m p a r i n g t h e r e l a t i o n T a I - T a I I w i t h t h e c o r r e s p o n d i n g relations in V and Nb, and b y a p p l y i n g t h e irregular d o u b l e t law in t h e iso-electronic systems W I I ~) and T a I. The r e - i n t e r p r e t a t i o n entails new a s s i g n m e n t s for t h e 5d36s(Sp)6plevels, b u t those of t h e 5d36s(SF)6p-levels and t h e 5d26s 2 6 p - c o n f i g u r a t i o n are p r a c t i c a l l y unaffected. Full j u s t i f i c a t i o n will be given in a s u b s e q u e n t paper. The ionization energy can n o w be e v a l u a t e d from the position of 5d 3 6s(SF) 7s 4F, if one knows the decrease of t h e q u a n t u m defects in going f r o m 6s 2 to 6sTs. I n c o n n e c t i o n w i t h related spectra a reasonable v a l u e of --
167
--
168:
STRUCTURE OF TANTALUM I SPECTRUM
A s is O. 10. A p p l y i n g t h i s t o t h e 4F612- a n d 4 F , t~-series w e f i n d t h a t t h e l o w e s t l e v e l o f T a I, 5 d 3 6 s 2 4173h, h a s a v a l u e o f (62700 + 700) c m - 1 w i t h r e s p e c t
t o T a I I 5da6s s17 I. I f t h i s is t h e l o w e s t l e v e l o f T a I I , a s is a s s u m e d i n t h e p r e l i m i n a r y a n a l y s i s o f t h a t s p e c t r u m 3), t h e i o n i z a t i o n p o t e n t i a l o f T a I • b e c o m e s ( 7 . 7 7 + o . x o ) V o l t . T h e r e a r e i n d i c a t i o n s , h o w e v e r , t h a t in T a I I a l o w - l y i n g 3t7 is still m i s s i n g . Some conspicuous high odd sextet levels can be associated only with the 7p-electron. The ionization energy given above leads to a decrease of the quantum defect of 0.03-0.05 for the second members of these p-series ; this seems quite reasonable. All n e w e v e n l e v e l s a n d s o m e o f t h e o d d o n e s h a v e b e e n l i s t e d in t a b l e I TABLE I New Levels in Ta I .~ Value
J
'/2
Even g Identification 0.92 5dS6s ~ 2C-71,
41151.2~ 1/od --0.6~ 1.0C 41594.7S 1.37, 42501.58 5/2 1.4C 43982.5C 212 1.3~ 45636.84 47319.49 h
;/.
46981.86 512 47817.1C
I I Value 18504.78 19178.40 5da6s(SF)7s eF~h 22380.49] ,, eF*h 22681.701 ,, eF% 25008.921 ,, eF, h 26936.11 ,, eF~h 30361.29 ,, eFn/~ 44689.28 44806.74 ,, 'tFs/t 4s255.851 !46409.77 147799.94 148808.56 50660.46
Odd J t/2
g
0.87 '1~ 9/. 1.2E u] 2 1.3C ta/2 s/.
tl/z 1.35
s/2 1.81 9/2 1.36
5/,
1.67
'/2 1.44 0/~ 1.36 3Is 5/.,
Identification •5d'-6s2(SF)6p *Dt h 5dS6s(SF)6p aG612 ,, ,, ,, ,, ,, 5d4(6D)6p ,, ,, ,, ~t
5d36s(SFJ7p
,,
s~ h
eG~/s eGttls
6G~/t aF~t/s UDslt 6F, I, UD~h ~DTIs
aD,It eD31~ eDs/~
Received 21-2-51. P . F . A. KLINKENBERG. G. J. VAN DEN B~RG. J . C. VAN DEN BOSCH. Zeeman-Laboratorium aer Universiteit van Amsterdam
REFERENCES 1) K l i n k e n b e r g , P. F. A., V a n d e n B e r g , G. J. and V a n d e n B o s c h , J. C.. Physica 16 (1950), 861. 2) L a p o r t e , O. and M a c k , J. E., Phys. Rev. 63 (1943), 246. 3) K i e s s , C. C., H a r r i s o n , G. R. and H i t c h e o c k , W. J., J. Res. Bur. Stand. 44 (1950), 245.