State-to-state relaxation of highly vibrationally excited acetylene by argon

Abstract

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+ν3+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.