YUSUKE OKABAYASHI, JIAN TANG, YUKI MIYAMOTO, KENTAROU KAWAGUCHI, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-Naka, Okayama 700-8530, Japan.
Time-resolved double resonance (TRDR) method has been used to study the rotational and vibrational relaxiation for a long time. However, the study of IR-IR TRDR in the 3µm region has been very limited due to the lack of powerful tunable IR lasers in this region. In the present study, we used a tunable pulsed OPO IR laser (6 mJ@6 ns, 0.2 cm-1 linewidth) and a tunable cw-OPO IR laser (up to 200 mW, 3 MHz linewidth) both in the 3µm region to study the IR-IR TRDR for the 4 and 2 4- 4 vibrational bands of CH3F.
The pulsed IR laser pumps CH3F from the ground state to a certain rotational level (J, K) of v4=1, and the cw IR laser probes this (J, K) level by the 2 4- 4 ladder transition. A time profile for the transition intensity of the probe line gives the T1 relaxiation time for the (J, K) level of v4=1. The pressure dependence of T1 for various (J, K) levels of v4=1 was obtained, which can be compared with the linewidth measurement for the 4 band of CH3F.