15min:

GARY V. LOPEZ, PHILIP M. JOHNSON, TREVOR J. SEARS, Department of Chemistry, Stony Brook University, Stony Brook, New York 11794; AND CHIH-HSUAN CHANG, Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973.

Cavity ring-down (CRD) measurements have been made on the S₁ (A ¹B₂) S₀ (X ¹A₁) absorption spectrum of slit jet-cooled phenylacetylene (PA) in the 279 nm region as a further investigation of the photophysical properties of PA reported by Hosftein et al. The intensities in the new CRD data are compared with those obtained in the old REMPI experiments, and computational models. The results show that the strong bands in the REMPI spectrum are attenuated while the weak bands (a₁ modes) remained the same when compared to CRD spectra. The comparison of the simulated spectrum to the CRD and REMPI spectra were satisfactory for most part when the a₁ modes were scaled up by a factor of 3.24 and 3.55, respectively, giving evidence of some possible theoretical artifacts.^c The temperature of the slit jet-cooled PA was found to be in the range of 30\pm5K by comparison with simulations of the rotational structure of the band origin of the S₁ S₀ transition. Additionally, many hot bands located near the band origin of the this transition have been assigned.

Acknowledgments: Work at Brookhaven National Laboratory was carried out under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy and supported by its Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences.