15min:

MITSUSHI OKUBO, MASATOSHI MISONO, JINGUO WANG AND HAJIME KATO, Molecular Photoscience Research Centre, Kobe University, Nada-ku, Kobe 657-8501, Japan; MASAAKI BABA, Faculty of Integrated Human Studies, Kyoto University, Kyoto 606-8501, Japan.

The Doppler-free spectrum and the Zeeman effect of the A ¹B_1u (v₄=1:b_1u) X ¹A_g(v=0) transition of naphthalene in the 33576.4-33578.0 cm^-1 range has been measured by means of two-photon absorption spectroscopy with counter propagating light beams of identical wavelength within an external cavity. Rotational lines were fully resolved, and 1098 ^Q(K)Q(J) lines of J=0-42, K=0-24 were assigned. The molecular constants of the A ¹B_1u(v₄=1:b_1u) state were determined. Deviations from the line positions calculated using the molecular constants were observed for several lines. Perturbations were not observed for K=0 but were observed to increase with increasing values of K. The perturbations were therefore identified as originating from a parallel Coriolis interaction. The Zeeman splittings for lines of a given J were observed to be maximum at K=0 and to decrease with increasing K. Analysis of these results indicate that the magnetic moment lies along the c axis (perpendicular to the molecular plane). Any lines broader than our instrumental resolution (5 MHz) were not observed at H=0 T. The J and K dependence of the Zeeman splittings of the A ¹B_1u(v₄=1:b_1u) X ¹A_g(v=0) transitions were observed to be regular. This observation and the small number of perturbed lines, leads to the conclusion that the resonance interaction of the A ¹B_1u state with the T₁ ³B_3u and T₂ ³B_1u states are small and negligible in the observed region.