SPECTROSCOPY OF VIBRATIONALLY EXCITED STATES OF CCH

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1995

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Ohio State University

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By laser-induced fluorescence (LIF), we previously detected 22 UV bands due to transitions from vibrationally excited states of $CCH(\tilde{X}^{2}\Sigma^{+})$ to $\tilde{B}^{2}A.^{1-3}$ Five new bands of parallel-type transitions are rotationally analyzed. The LIF spectrum of the 35929, 36658 and $36821 cm^{-1}$ bands were obtained after photolysis at 193 nm of a supersonic beam of argon seeded with acetylene; two other bands at 38360 and $38452 cm^{-1}$, assigned as $S \leftarrow \tilde{X} (0,2^{0},0)$ and $V \leftarrow \tilde{X} (0,2^{2},0)$, were recorded after photolysis at 193 nm of a mixture of acetylene and $SF_{6}$ at high pressure. States S and V represent K=0 and 2 stacks of a single vibrational level T, located at $39157.4126(51) cm^{-1}$, of $\tilde{B}^{2} A$. Gating at the fluorescence lifetime enables us to separate weak bands of CCH from $C_{2}$. Methods of obtaining vibrationally cooled CCH will be discussed.

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1. Y.-C. Hsu, J. J.-M. Lin, D. Papoušek, and J.-J. Tsai, J. Chem. Phys. 98, 6690(1993). 2. Y.-C. Hsu, Laser Techniques for State-Selected and State-to-State Chemistry II Proceedings of SPIE conference, 2124, 302(1994). 3. Y.-C. Hsu, Y.-J. Shiu and C.-M. Lin, J. Chem. Phys. (to be submitted).
Author Institution: Academia Sinica, P. O. Box 23-166, Taipei 107, Taiwan, Republic of China.; National Taiwan University, Taipei 107, Republic of China.

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