15min:

HONG-YU SHI, LI-HONG XU, R. M. LEES, Centre for Laser, Atomic and Molecular Sciences (CLAMS), Department of Physics, University of New Brunswick, Saint John, NB, Canada E2L 4L5; D. W. TOKARYK, CLAMS, Department of Physics, University of New Brunswick, Fredericton, NB, Canada E3B 5A3; A. R. W. MCKELLAR, Steacie Institute for Molecular Sciences, National Research Council, Ottawa, ON, Canada K1A 0R6; D. R. T. APPADOO, Canadian Light Source, 101 Perimeter Road, University of Saskatchewan, Saskatoon, SK, Canada S7N 0X4.

The ₁₁ fundamental and the ₁₆ + ₁₈ - ₁₈ hot band have been identified in the high-resolution Fourier transform spectrum of trans-acrolein (CH₂=CH-CH=O) recorded in the 10-µm region on the Far-Infrared beamline of the Canadian Light Source synchrotron in Saskatoon. The two bands are centered at 912 cm^-1 and 957 cm^-1, respectively, with the excited ₁₁ state corresponding to the A' in-plane CH₂-rocking mode and the ₁₆ + ₁₈ state to the combination of the A'' out-of-plane CH₂ rock with the low-frequency (158 cm^-1) A'' C-C torsional mode.This extends our previous work on the ₁₄ and ₁₆ fundamentals centered at 993 and 959 cm^-1, leaving only the ₁₅ mode now to be assigned at high resolution in the 10-µm spectral region for this important atmospheric pollutant. The ₁₁ band is type a/b and the ₁₆ + ₁₈ - ₁₈ hot band is c-type, so that assignments could be confirmed by lower-state combination differences. The assigned transitions have been fitted to a Watson asymmetric rotor Hamiltonian, and molecular parameters for both states will be reported.