Time resolved spectroscopy of jet-cooled acetone

The authors have recently reported the study of time resolved emission from single vibronic levels of jet-cooled acetone. This paper presents a more detailed description of the experiments conducted to date. The results show that decay times were approximately, but not strictly, exponential. In particular, a long-lived emission component appears to be present, and is more pronounced in acetone-d6 than in acetone-h6. The decay times measured in argon are longer than those observed with helium as a carrier gas. The isotropic effect is quite large--decay times in the deuterated molecule are about three times longer than in the protonated one. The decay rate decreases as the excitation energy is increased up to 1000 cm-1 excess energy, remained roughly constant from that energy up to 2000 cm-1, then rose again. Further increase in energy does not affect the decay rate, but the intensity appears to reach a maximum at an excess energy of about 3000 cm-1 and then decreases