FD11 15min11:28
THE EFFECTS OF TRIPLET PERTURBERS ON PHOTOPHYSICAL PROCESSES IN ACETYLENE.

STEPHEN DRUCKER, JONATHAN P. O'BRIEN, PARESH PATEL AND ROBERT W. FIELD, MIT, 77 Massachusetts Avenue, Cambridge, MA 02139.

We have recorded excitation spectra of the acetylene A 1Au <- X1Sigmag+ transition by measuring simultaneously the total emission in two spectral regions: UV (200-400 nm) and NIR (0.9-1.5 µm). UV emission is due to well-characterized1 A -> X transitions. The source of the NIR signal is suggested by the emission patterns within the subbands studied, V02 K01 and V03 K01. (V denotes the trans -bending mode.) The NIR:UV intensity ratio is approximately constant throughout the V02 K01 subband. This is consistent with excited C2H or C2 as the carrier of the NIR signal, because these species, capable of emitting in the NIR2,3, could be produced via multiphoton processes2 resonantly enhanced by the A state as intermediate. The V03 K01 subband shows significantly more fluctuation in the NIR:UV intensity ratio than does the V02 K01 subband. The one-quantum increase in trans -bending excitation enables accidental resonances with background states to modulate the NIR emission pattern. Triplet perturbers could participate in this process by modifying the resonance enhancement of C2H or C2 production. Mixed S1--triplet states could additionally contribute to the NIR signal through Tn -> T1 (n > 1) transitions.

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1\RefK. Yamanouchi, N. Ikeda, S. Tsuchiya, D. M. Jonas, J. K. Lundberg, G. W. Adamson, and R. W. Field\JCP9563301991

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2\RefY.-C. Hsu, M.-S. Lin, and C.-P. Hsu\JCP9478321991

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3\RefF. Shokoohi, T. A. Watson, H. Reisler, F. Kong, A. M. Renlund, and C. Wittig\JPC9056951986