STATE-TO-STATE RELAXATION OF HIGHLY VIBRATIONALLY EXCITED ACETYLENE BY ARGON

Vibrational overtone excitation followed by laser-induced fluorescence (LIF) interrogation determines state-to-state rotational and vibrational relaxation rates of highly energetic acetylene molecules by argon. We initially excite a single rotational state of the vibration 3ν3 (three quanta of C-H stretch, Evib=9640 cm-1) and detect the state (3ν3, Jf=20) in rotational relaxation measurements or the state (ν1+ν2+ν 3+2ν4, l=0, Jf=4) in vibrational relaxation measurements. The data, which we acquire under single-collision conditions, show that argon rotationally relaxes acetylene almost half as efficiently as acetylene itself but is relatively inefficient in vibrational relaxation. © 1994 American Institute of Physics.