THE EFFECTS OF TRIPLET PERTURBERS ON PHOTOPHYSICAL PROCESSES IN ACETYLENE

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Title: THE EFFECTS OF TRIPLET PERTURBERS ON PHOTOPHYSICAL PROCESSES IN ACETYLENE
Creators: Drucker, Stephen; O'Brien, Jonathan P.; Patel, Paresh; Field, R. W.
Issue Date: 1996
Publisher: Ohio State University
Abstract: We have recorded excitation spectra of the acetylene $\tilde{A}A_{u}\leftarrow \tilde{X}^{1}\Sigma^{+}_{u}$ transition by measuring simultaneously the total emission in two spectral regions: UV (200-400 nm) and NIR (0.9-1.5 $\mu$m). UV emission is due to well characterized $\tilde{A}\rightarrow \tilde{X}$ transitions. The source of the NIR signal is suggested by the emission patterns within the subbands studied, $V_{o}^{2}K_{0}^{1}$ and $V_{0}^{0}K^{0}_{0}$. ($V$ denotes the trans-bending mode.) The NIR:UV intensity ratio is approximately constant throughout the $V_{0}^{2}K_{0}^{1}$ subband. This is consistent with excited $C_{2}H$ or $C_{2}$ as the carrier of the NIR signal because these species, capable of emitting in the $NIR_{2}$,3 could be produced via multiphoton $processes^{2}$ resonantly enhanced by the $\tilde{A}$ state as intermediate. The $V_{0}^{3}K_{0}^{1}$ subband shows significantly more fluctuation in the NIR:UV intensity ratio than does the $V_{a}^{2}K_{a}^{1}$ subband. The one-quantum incvrease in trans-bending excitation enables accidental resonances with backround states to modulate the NIR emission pattern. Triplet perturbers could participate in this process by modifying the resonance enhancement of $C_{2}H$ or $C_{2}$ produciton. Mixed $S_{1}$-triplet states could additionally contribute to the NIR signal through $T_{u}\rightarrow T_{l}(\pi > l)$ transitions.
Description: $^{1}$K. Yamanouchi, N. Ikeda. S. Tsuchiya, D. M. Jonas, J. K. Lundberg, G. W. Adamson, and R. W. Field, J. Chem. Phys. 95, 6330 (1991). $^{2}$Y.-C. Hsu, M.-S. Lin, and C.-P. Hsu, J. Chem. Phys. 94, 7832 (1991). $^{2}$F. Shokoohi, T. A. Watson, H. Reisler, F. Kong, A. M. Renlund, and C. Wittig, J. Phys. Chem. 90, 5695 (1986).
Author Institution: MIT
URI: http://hdl.handle.net/1811/13419
Other Identifiers: 1996-FD-11
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