Single Vibronic Level Fluorescence. II. Vapor-Phase Fluorescence Spectra from the Zero-Point Level of B2u1 Benzene and Benzene-d6

Abstract

Fluorescence spectra have been obtained at 300°K from C6H6 and from C6D6 vapor at 0.1 torr in which all emitting molecules are in the zero-point vibrational level of the B2u1 state. Analysis of the spectra are completed using selection rules appropriate for D6h symmetry of both the ground (1A1g) and excited (1B2u) states. The spectra are compared with the zero-point fluorescence obtained by the conventional method of matrix isolation of benzene at 77°K. The forbidden transitions seen in the latter are absent in isolated molecule gas-phase spectra. The zero-point spectra are also compared with that from a 300°K Boltzmann distribution of B2u1 vibronic levels.

A new sensitive detection scheme for helium nanodroplet isolation spectroscopy: application to benzene

“…The fluorescence quantum yield of the vibrationless and the 6 1 level in the 1 B 2u state have been determined to be 0.22 and 0.27, respectively. 31 It is generally accepted that intersystem crossing to the T 1 3 B 1u is the main cause for the low fluorescence quantum yield. This lowest triplet state is located 3.67 eV above electronic ground state.…”

Lifetimes in Excited States

“…This is a most promising technique for the direct measurement of rate con stants for intersystems crossing in the presence of other radiationless processes such as photochemical decomposition. spectrum can be distorted due to reabsorption of the emitted radiation, in which case the spectrum generated with a transparent thermalizing gas will differ from the spectrum of the pure substance (292). In the region of 0.…”

Extended view of the benzene 260-nm transition via single vibronic level fluorescence. I. General aspects of benzene single vibronic level fluorescence

“…The second examined the structure of fluorescence from the zero-point levels of C6He and CeDe. 14 Another used SVL fluorescence as an aid in assigning the low-pressure fluorescence from benzene excited with the 2537 Á Hg line. 15 Finally, an example of the use of SVL fluorescence spectra to elucidate absorption band assignments is included in a review of excited state relaxation in benzene.…”