title: Alignment selection of the metastable CO(a 3Π1) molecule and the steric effect in the aligned CO(a 3Π1) + NO collision.
abstract: The aligned metastable CO(a (3)Π1) molecular beam was generated by an electronic excitation through the Cameron band (CO a (3)Π1 ← X (1)Σ(+)) transition. Beam characterization of the aligned molecular beam of CO(a (3)Π1) was carried out by (1 + 1) REMPI detection via the b (3)Σ(+) state. The REMPI signals showed the clear dependence on the polarization of the pump laser, and the experimental result was well reproduced by the theoretical simulation. This agreement confirms that aligned metastable CO(a (3)Π1) can be generated and controlled by rotating polarization of the pump laser. By using this technique, a single quantum state of CO(a (3)Π1) can be selected as a metastable molecular beam. The steric effect in the energy-transfer collision of CO(a (3)Π1) with NO forming the excited NO was carried out with this aligned CO(a (3)Π1) molecular beam. We find that the sideways orientation of CO(a (3)Π1) is more favorable in the formation of the excited NO(A (2)Σ(+), B (2)Π) than that for the axial collisions. The obtained steric effect was discussed with the aid of the spatial distribution of CO(a (3)Π1) molecular orbitals, and we find that specific rotational motion of CO(a (3)Π1) in each state may not be a dominant factor in this energy-transfer collision.
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Nakamura
authors.forename: Dock-Chil
authors.initials: DC
authors.lastname: Che
authors.forename: Po-Yu
authors.initials: PY
authors.lastname: Tsai
authors.forename: King-Chuen
authors.initials: KC
authors.lastname: Lin
authors.forename: Toshio
authors.initials: T
authors.lastname: Kasai