Generation of coherent anti-Stokes rotational Raman radiation in hydrogen gas

Coherent anti-Stokes rotational Raman scattering (CARS) has been observed for the J=3→5 rotational transition in hydrogen at a Raman frequency shift of 1033.4 cm−1. The pump wavelength of 532.1 nm was provided by a frequency-doubled acousto-optic Q-switched cw krypton-arc-lamp-pumped Nd:YAG laser, and the Stokes radiation at 563.1 nm was generated by a rhodamine 6G jet-stream dye laser excited by the 532.1-nm radiation. A comparison is made of the H2 rotational CARS signal with the vibrational CARS signal produced by the 995.4-cm−1 ν2 vibrational mode of benzene.