DIMETHYL-S-TETRAZINE VAPOR: VISIBLE ABSORPTION, LASER-EXCITED FLUORESCENCE, AND PHOTOPHYSICS
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Date
1980
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Ohio State University
Abstract
Except for broader bands, hot bands and a $500 cm^{-1}$ shift of the 0-0 band to higher frequencies, dimethyl-s-tetrazine as a vapor is found to exhibit the same visible absorption and excited-state zero-level emission spectra that it does when dissolved in p-xylene at $4.2^{\circ} K$ and below. Vibrational frequencies in both $\tilde{A}^{1} B_{3u}$ and $\tilde{X}^{1}A_{g}$ states show almost no solvent affects. Even an unusual ""negative"" anharmonicity of the principal progression-forming mode $\nu_{6a}$ in the ground state is the same in both phases. Franck-Condon activity also is independent of phase; in fact, for $\nu_{6a}$ it is nearly the same as for s-tetrazine in the vapor phase. Single vibronic level excitations into the $0-0, 6a^{1}_{0}, 1^{1}_{0}$ and $6a^{2}_{0}$ bands show that vibrational relaxation is appreciable for pressures of a torr and greater. Mode-to-mode flow does not follow the propensity rules exhibited by the $S_{1}$ state of benzene. Rotational relaxation and competition of collisional relaxations with predissociation are revealed when foreign gas is added.
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