			15min:

TIME-RESOLVED IR-IR DOUBLE RESONANCE FOR THE

₄ and 2

₄-

₄ VIBRATION-ROTATION TRANSITIONS OF CH₃F.

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, sim 0.2 cm^-1 linewidth) and a tunable cw-OPO IR laser (up to 200 mW, sim 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.