Identification of hot band transitions of CH4 near 3000 cm−1

Rovibrational transitions between vibrationally excited states of 12CH4 in the 3.4 μm wavelength region are investigated by a pump-probe technique using an optical parametric oscillator as a pump and a tunable diode laser as a probe. Methane molecules are excited into selected levels of the 2ν3 state of the tetradecad and numerous transitions between pentad and tetradecad, and between tetradecad and triacontad, have been observed in this spectral range. Positions and assignments of transitions involving a level of the 2ν3 (F2) substate are reported. Reliable energy values for 2ν3 (F2) levels up to J = 6 are obtained, and the energies and assignments of a number of 3ν3 levels have been deduced allowing identification of IR lines in the 1.1 μm region.