10min:

M. SUZUKI, T. YAMASHITA, T. OHTSUKA, T. YUKIYA AND N. NISHIMIYA, Dept. of Electronic Engineering, Tokyo Institute of Polytechnics, Iiyama 1583, Atsugi City, 243-0297 Kanagawa, Japan.

\hspace3em The vib--rotational spectrum of the 2₁+₅^l=1, ₁+₂+3₅^l=1, and 2₂+5₅^l=1 combination bands of acetylene was measured using a GaAs semiconductor laser (New Focus 6148) at the wavenumber region from 7400 to 7600 cm^-1 and the P --, R -- and Q --branches were assigned. The wavenumber measuring system with a wavelength meter (Anritsu MF9630A) and a confocal interferometer of 15 cm was calibrated against the H₂O lines. ¹ The formulation describing the spectral line positions by a third order polynomial of J ( J +1) with the effective spectroscopic parameters of ₀^eff, B_v^eff, D_v^eff, and H_v^eff was obtained using second order perturbation theory to take the l --type resonance effect into consideration. The spectroscopic constants and the l --type doubling constants were calculated from the effective rotational parameters determined using a least squares fitting procedure for the e -- and f --levels by the aid of the molecular constants reported by ref. 2 and 3.

\underline\makebox[8cm]

1. R.A.Toth, \sl Appl.Opt., 33, 4851 (1994).
2. M.Herman, T.R.Huet, Y.Kabbadj, and J.V.Auwera, \sl Mol.Phys., 72, 75 (1991).
3. J.J.Hillman, D.E.Jennings,G.W.Halsey,S.Nadler,and E.W.Blass, \sl J.Mol.Spectrosc., 146, 389(1991).