Rovibrational energy transfer in the 4v_CH manifold of acetylene viewed by IR-UV double resonance spectroscopy. 2. Perturbed states with J = 17 and 18

Collision-induced state-to-state molecular energy transfer between rovibrational states in the 12 700 cm^-1 4v_CH manifold of the electronic ground state X~ of acetylene (C₂H₂) is monitored by time-resolved infrared-ultraviolet double resonance (IR-UV DR) spectroscopy. Rotational J-states associated with the (v₁ + 3v ₃) or (1 0 3 0 0)⁰ vibrational combination level, initially prepared by an IR pulse, are probed at ~299, ~296, or ~323 nm with UV laser-induced fluorescence via the A electronic state. The rovibrational J-states of interest belong to a congested manifold that is affected by anharmonic, l-resonance, and Coriolis couplings, yielding complex intramolecular dynamics. Consequently, collision-induced rovibrational satellites observed by IR-UV DR comprise not only regular even-?J features but also supposedly forbidden odd-?J features. A preceding paper (J. Phys. Chem. A 2003, 107, 10759) focused on low-J-value rovibrational levels of the 4v_CH manifold (particularly those with J = 0 and J = 1) whereas this paper examines locally perturbed states at higher values of 7 (particularly J = 17 and 18, which display anomalous doublet structure in IR-absorption spectra). Three complementary forms of IR-UV DR experiments (IR-scanned, UV-scanned, and kinetic) are used to address the extent to which intramolecular perturbations influence the efficiency of J-resolved collision-induced energy transfer with both even and odd ?J. © 2005 American Chemical Society.