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A New Approach to the Vibronic Spectra of Molecular Crystals
Author(s) -
Broude V. L.,
Rashba E. I.,
Sheka E. F.
Publication year - 1967
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.19670190140
Subject(s) - excitation , molecular vibration , chemistry , crystal (programming language) , absorption band , absorption spectroscopy , spectral line , atomic physics , resonance (particle physics) , absorption (acoustics) , molecular physics , molecule , materials science , physics , optics , quantum mechanics , organic chemistry , computer science , programming language , composite material
A study is made of the experimental consequences of the theory of the vibrational spectra of molecular crystals presented recently in [3]. A discussion is also given of the model used in this theory. A detailed comparison is made between the theory and experimental results for pure and isotropic doped naphthalene crystals in the M‐band region. The theory accounts for the decay of electronic‐vibrational intra‐molecular excitations into pure electronic and intra‐molecular vibrational excitations by a resonance interaction. In this case the crystal spectrum should exhibit a wide absorption band corresponding to two‐particle excitation. If the reduction of the vibrational frequencies of the molecule accompanying its electronic excitation is comparable with the pure electronic excitation band width, the spectrum should also show a narrow band corresponding to a one‐particle excitation. These bands should be associated with the vibrational band which is observed experimentally. This idea is used to analysis the absorption in the first vibrational transition region of a naphthalene crystal. The one‐ and two‐particle excitation regions are identified and a quantitative analysis of the data is made which is in accordance with the theory. Collective effects, connected with the excitation decay, appear to be important in this transition region. In this connection of particular interest is an analysis of peculiarities of impurity vibrational absorption in isotopic solutions. Comparison between the spectral data naphtalene deutero‐isotopes and the theory also indicates the importance of some complicated collective interactions.