Analysis of the low temperature fluorescence and phosphorescence spectra of p-difluorobenzene

Abstract

The low temperature fluorescence spectra (4.2 K) of solid solutions of pditluorobenzene-h., (pDFB-h.,) and-& have been recorded and analyzed. The absence of fluorescence from vibrationally excited states at 4.2 K eliminates the sequence and "hot band" structure which complicate the analysis of the vapor fluorescence spectrum. On the basis of a comparison of our vibrational analysis with those published for the vapor phase fluorescence, several incorrect assignments in the latter have been identified. The high resolution and lack of spectral congestion obtained in the low temperature matrix isolated fluorescence spectra also allowed additional vibrational assignments to be made. These results are of added importance because of the extensive use. which has been made of pDFR for radiationless relaxation studies in the vapor phase. The phosphorescence spectrum of crystalline pDFB-h, was observed with sufficient intensity to locate the electronic origin to make several vibrational assignments. Additionally, the zero-field splitting of the first triplet excited state was measured by optically detected magnetic resonance techniques.

Consistent assignment of the vibrations of symmetric and asymmetric para-disubstituted benzene molecules

“…Generally, the fundamental vibrational wavenumbers derived in the earlier studies are in good agreement with the most recent vapour-phase IR/Raman study by Zimmerman and Dunn in 1985 [15]. This paper also makes frequent reference to unpublished electronic spectroscopy results, which do not appear to have been published since then; although there is an earlier published fluorescence study of solid samples at 4 K by one of the authors [16]. The assignments in Ref.…”

“…Thus, there is much mixing and wavenumber order change in these b 1 vibrations. In terms of the M i labels a similar story holds, although we note that modes M 16 and, surprisingly,  18b .…”

The R2PI Spectroscopy of Tyrosine: A Vibronic Analysis

“…Since then, much work has been done concerning both the ground-state and excited-state spectroscopy of benzenes substituted in various ways (7,8,(17)(18)(19)(20)(21)(22)(23). The only systematic study of the ground-state spectroscopy of para-substituted phenols, however, appears to be that of Jakobsen and Brewer (24).…”

Intra- and Intermolecular Vibrational Energy Relaxation of C−H Overtone Excited Benzonitrile,para-Difluorobenzene, and Pyrazine in Solution

“…The complex structure at the excitation wavelength around 2330 nm we attribute to transitions from the ground state to 1ν x 1ν y ( x = 1, 2−4, y = 8, 9−13). In the condensed phase, the (0, 0)-band of the S 1 ← S 0 transition in pDFB is located at 274 nm . ν 11 and ν 18 appear to be the FC active modes …”