REMPI-Doppler Spectroscopy of H Atoms with Tunable VUV Radiation around Lyman a Line

Abstract

With the use of a tunable and coherent vacuum ultraviolet (VUV) radiation around Lyman-α line, a spectroscopy combining the resonantly enhanced multiphoton ionization with the Doppler spectroscopy (REMPI-Doppler spectroscopy) was investigated. The method was applied to the detection of hot hydrogen (H) atoms photodissociated from hydrogen iodine (HI) molecules. Corresponding to whether the transition is parallel or perpendicular, the velocities of recoiling H atoms were measured to be 1.12×10⁴ m/s for parallel transition dissociating to [H(²S_1/2)+I^*(²P_1/2)], and 1.75×10⁴ m/s for perpendicular transition dissociating to [H(²S_1/2)+I(²P_3/2)], respectively. Atomic H beams formed via purely parallel or perpendicular transition were extracted to measure the velocity spreads of the beam. Experimental velocity distributions were fitted well to the theoretical curves calculated by taking account of appropriate rotational and translational motions of parent HI molecules.