10min:
DIRECT OBSERVATION OF THE 2 3 Piu STATE OF Rb2 IN A PULSED MOLECULAR BEAM: ROTATIONAL-BRANCH INTENSITY ANOMALIES IN THE 2 3 Piu(1u) - X 1 Sigmag+(0g+) BANDS.

Y. LEE, Y. YOON, S. J. BAEK, D-L JOO, J-S RYU AND B. KIM, Department of Chemistry, Korea Advanced Institute of Science and Technology, Taejon 305-701, Korea.

The first observation of 2 3 Piu - X 1 Sigmag+ transitions is reported. Rotationally resolved transitions of the 2 3 Piu(1u) - X 1 Sigmag+(0g+) and 2 3 Piu(0u+) - X 1 Sigmag+(0g+) are observed by resonance enhanced 2-photon ionization (RE2PI) method in a pulsed molecular beam. Omega-doubling and interference induced rotational branch intensity anomalies are observed for 2 3 Piu(1u) - X 1 Sigmag+(0g+) transitions. Both of 2 3 Piu(0u+) and 2 3 Piu(1u) states are strongly mixed with singlet states by spin-orbit coupling. The former with 2 1 Sigmau+ and the latter with 2 1 Piu. In relatively weak 2 3 Piu(1u) bands P-branch rotational lines disappear and the intensities of R-branch rotational lines are enhanced. These intensity anomalies in 2 3 Piu(1u) - X 1 Sigmag+(0g+) transition, due to an interference effect between parallel and perpendicular transition amplitudes, is caused by Delta Omega = \pm1 perturbation. The molecular constants of 2 3 Piu(0u+) - X 1 Sigmag+(0g+) transition are determined as Te = 19784.2588 \pm 0.0088 cm-1, omegae = 42.1954 \pm 0.0060 cm-1, omegaexe = 0.1701 \pm 0.0011 cm-1, omegaeye = -0.001096 \pm 0.000057 cm-1, Be = 0.018503 \pm 0.000018 cm-1 for 85Rb2. The spin-orbit coupling constant A and Omega-doubling parameters p and q are determined by simultaneous fitting of the rotational contours of both 2 3 Piu(1u) - X 1 Sigmag+(0g+) and 2 3 Piu(0u+) - X 1 Sigmag+(0g+) transitions.