D D Pant
Articles written in Proceedings – Section A
Volume 18 Issue 5 November 1943 pp 309-326
A general survey of the known luminescence spectra of crystals is given. Those which give discrete spectra have been divided into seven classes. The luminescence spectrum of each of these crystals is examined to see what evidence it gives regarding the nature of the vibrations in the crystal lattices. Wherever possible the information thus obtained is supplemented by the evidence furnished by the complementary absorption spectra. It is shown that there is a mass of striking evidence indicating that vibrational frequencies are sharp and monochromatic in all crystals. Those luminescence spectra, which are not discrete are due to an electronic transition in which one or both the electronic states involved are not sharp and hence no evidence regarding the vibrational frequencies can be gained from them. It is remarkable that over the whole range of crystal structure—from the typical covalent crystal diamond to the typical Van der Waals crystal solid nitrogen— the vibrational frequencies are all sharp and monochromatic. The ionic crystals,
Volume 19 Issue 3 March 1944 pp 135-140
The fluorescence spectrum of solid uranyl fluoride has been studied at liquid-air temperature. The spectrum which consists of 17 sharp and discrete bands is classified into 5 groups and 5 series. The bands have been interpreted as being due to the transitions from (0, 0, 0)′ and (0, 1, 0)′ levels to the various vibrational levels of the ground state. All the three frequencies of the uranyl ion have been taken into account for the interpretation.
Volume 22 Issue 2 August 1945 pp 95-109
The fluorescence spectra at liquid-air temperature of crystalline uranyl chloride, uranyl fluoride I and II, and of uranyl bromide have been studied for the first time. The spectra of uranyl acetate, nitrate, sulphate and uranyl potassium sulphate have been taken for comparison. Out of the several series present, B, C, D and E are pointed out to be most important. A remarkable shifting of the D band as well as peculiarities in the intensity distribution are noticeable. The similarity between the C and E bands and the extended diffuseness produced by the D bands are also noteworthy.
A slight rise in temperature from −185°C. causes a great increase in the diffuseness produced by the D bands. With moist crystals the D band appears as a short continuum even at −185° C. but at −110° C. and −70°C. only B, C and E are present, the D bands completely disappear. Uranyl bromide has been found to increase tremendously in intensity on cooling, its spectrum at −185° consisting of very broad bands giving an appearance of a continuous spectrum.
The absorption spectra of uranyl chloride have been taken with varying thickness of the absorbing layer. With thick layers, some bands which are observed in fluorescence can also be obtained in absorption. In the absorption spectrum of uranyl fluoride II and uranyl bromide the first two A and B bands of the fluorescence spectra appear as A and B band in absorption with a remarkable reversal of intensity.
Volume 22 Issue 2 August 1945 pp 110-121
From some direct experimental evidence, it is concluded that the entire fluorescence spectrum of the uranyl salts arises out of a transition from a single excited state (designated1
Volume 31 Issue 1 January 1950 pp 35-41
Volume 31 Issue 2 February 1950 pp 103-106
The effect of temperature on the intensity of the
Volume 50 Issue 5 November 1959 pp 323-335
The fluorescence spectra of uranyl nitrate solutions at room temperature are shown to give four distinct series of bands, designated
Volume 51 Issue 2 February 1960 pp 60-74
Photometric studies on the fluorescence spectra of rapidly cooled aqueous and alcoholic solutions of uranyl nitrate are reported. Five distinct series of bands, designated as
Volume 69 Issue 6 June 1969 pp 324-337
Volume 70 Issue 5 November 1969 pp 221-233
The absorption spectra of new crystalline uranyl complexes with pyridine, at 80° Kare described. Pyridine uranyl chloride crystallises in two forms, both forms give sharp line like bands at low temperatures. In Form I the bands are analysed in terms of five electronic transitions F, M, D, U and SU of which the former four were suggested for uranyl ion by Dieke
Volume 71 Issue 5 May 1970 pp 201-208
The fluorescence spectra of uranyl complexes with pyridine are described and compared with the known spectra of double salts and addition compounds. In some cases the spectra are of the double salt type whereas in others of the type of addition compounds. The fluorescence spectra of uranyl salts have been generalised into three categories,