Showing papers in "Journal of Applied Spectroscopy in 1971"

A study of the electron processes occurring during excitation of steady state luminescence and phosphorescence of calcium tungstate

Abstract: A number of papers dealing with the reasons for the prolonged afterglow induced by x rays and cathode rays in calcium tungstate has been published in recent years . Light-sum accumulation does not occur under excitation by the 254 nm m e r c u r y line. It was assumed in [1-3] that this difference between the effect, on the one hand of x rays and cathode rays and, on the other, the line )~ = 254 nm, may be due to the formation in the f i rs t case of radiation defects which act as trapping centers. Since a fair ly intense and prolonged afterglow, however, is excited by ve ry small doses of x rays , it was assumed in [4] that the cause of this difference is that the quantum energy of the UV rays with a wavelength of 254 nm is insufficient to ionize the luminescence centers . In order to clarify the situation and also to obtain the informat ion which would be the basis of a solution to the problem of constructing an energy model for ca l cium tungstate, we measured the phosphorescence excitation and s teady-sta te luminescence spectra of CaWO 4 luminophors over a wide range of quantum energies f rom 4 to 21 eV. The method described in [5, 6] was used for this purpose.

IR and UV spectea of diaminodiphenylmethane isomers and the corresponding diisocyanates

Abstract: In the 3500-3200 cm -I region, the isomers of DA (Fig. la) have four (KBr tablets) bands of NH vibrations which are similar in character and frequency: 3450, 3420, 3345, 3220; 3445, 3415, 3340, 3220; 3470, 3420, 3348, 3227; and 3431, 3401, 3323, 3218 cm-irespectively for the4,4 t-, 3,3 T-, 2,2 T-, and 2, 4 ' i s o m e r s . The two h i g h f r e q u e n c y bands a r e the r e s u l t of the s p l i t t i n g of a band of NH 2 a n t i s y m m e t r i c v i b r a t i o n s . The bands in th is r e g i o n a r e c o m p l e t e l y r e t a i n e d in the S p e c t r a of s a m p l e s d i s p e r s e d in m i n e r a l oi l . The l a t t e r i n d i c a t e s that the s p l i t t i n g i s not due to the i n t e r a c t i o n of the s u b s t a n c e with the p o t a s s i um b r o m i d e . In ca rbon t e t r a c h l o r i d e so lu t i on (C = 0 .005-0 .01 m o l e / l i t e r , l = 10 m m ) , the s p l i t t i n g d i s a p p e a r s and a g roup of t h r e e bands i s o b s e r v e d in the s p e c t r a fo r e ach of the compounds : 3483, 3397, 3205; 3485, 3400, 3205; 3475, 3390, 3210; and 3475, 3395, 3208 cm -1 fo r 4 , 4 ' , 3 , 3 ' , 2 , 2 ' , and 2 , 4 ' D A r e s p e c t i v e l y . It is m o s t p r o b a b l e that in this c a s e , the s p l i t t i n g is due to h y d r o g e n bonds or to the e f fec t of the e l e c t r i c f ie ld of the c r y s t a l l a t t i c e . The band at ~3200 cm -1 may be a s s i g n e d to the o v e r t o n e of the s c i s s o r i n g bend ing v i b r a t i o n s of the NH 2 group . The i n c r e a s e in the r e l a t i v e i n t e n s i t y of the band a t ~3200 cm t in the so l id phase i s e v i d e n t l y due to F e r m i r e s o n a n c e with the v i b r a t i o n a l band of the bonded NH 2 g r o u p s . The 1630 cm -1 band for 4 , 4 ' D A , the doub le t s with p = 1625, 1600 and 1634, 1618 cm t fo r 3, 3 ' and 2, 2 TDA r e s p e c t i v e l y , and the 1630 cm t band fo r 2 , 4 t D A , a l l c o r r e s p o n d to s c i s s o r i n g be nd ing v i b r a t i o n s of the a m i n o g r o u p s . The bands fo r the CN g roups in the DA i s o m e r s a p p e a r in the 1250-1310 cm -1 r a n g e .