Reflection spectra and optical parameters of alkali nitrates at 3?23 eV

Autor: N. I. Aleshkevich, V. G. Sholokh, E. F. Titkov, G. F. Dobrzhanskii
Rok vydání: 1983
Předmět:
Zdroj: Journal of Applied Spectroscopy. 39:1144-1146
ISSN: 1573-8647
0021-9037
DOI: 10.1007/bf01100374
Popis: Electronic absorption spectra have been recorded for thin films of alkali nitrates at 5-23 eV [I]. The UV and Si observed at 4 and 6 eV have been interpreted as n § ~* and ~ § ~* transitions [2, 3] in the NO~ group (Fig. i). The absorption bands in the region of i0 ($2) and 12 ($3) eV have been assigned [i] to charge-transfer transitions due to excitation of n and ~ electrons to a cation level in the corresponding alkali-metal atom. It is considered that the bond between the alkali cation and the NO~ group is purely ionic, which may be due to the ionization potentials of the alkali metals (Table i) [4] being substantially less than the value of about 13.6 eV for the oxygen atom. In that case, it is assumed that the nature of the cation should not affect the mutual disposition of the n and ~ levels in the valency band and consequently the energy difference between the $3 and S= transitions. Within the errors of experiment, the $3 -$2 difference was found as constant [i]. In this model, the position of the cation level should move downwards in energy in accordance with the ionization potential of the alkali metal in the series Cs < Rb < K < Na (Table i). However, the results obtained in that paper conflict with this conclusion, and it is therefore necessary to refine the model for the electronic structures of the alkali nitrates. Also, there are difficulties in operating with thin films, so it is necessary to check the results of [i]. For this purpose one can use the reflection spectra of the crystals. At present, data are available only for NaNOs [5], so one cannot perform a final identification of the electronic states of the nitrates in the high-energy region. Also, the literature lacks experimental data on the position of the absorption band in the region of 4 eV.
Databáze: OpenAIRE
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