Multiphoton Ionization and Dissociation of Metastable Molecular Species

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The following studies (1-4) were made.1. Multiphoton ionization (MPI) processes of trimethylamine (TMA) and triethylamine (TEA) via Rydberg states. For TEA, a 2+1 MPI process was studied by excitation with a dye laser, and the energy level of the vibrationless <S_2> state was determined. For TMA, a 1+1 MPI process via a vibrationally excited <S_2> level with the anti-stodes light of 2nd harmonic of an <Nd^(2+)> : YAG laser revealed the occurrence of competitive process of the ionization from the prepared <S_2> state ( <S(_2^*)> ) and that from the vibrationally excited <S(_1^(double-dagger))> state which resulted from the internal conversion <S(_2^*)> -> <S(_1^(double-dagger))> .2. Dissociation from a highly excited repulsive state of <I_2> produced by optical triple resonance. This process was monitored with the emission at 206.3 nm from the <I^*> atom given by dissociation. A potential energy curve of one of the <1_u> states which yield <I^*> +I was obtained by a simulation procedure.3. MPI of thioformaldehyde via the <-!C^1> <B_2> (4s <- n) Rydberg state. The MPI spectrum of thioformaldehyde via the C state was obtained by a 2+2 MPI excitation with a dye laser. A simulation of the rotational structure of the MPI spectrum revealed the effect of molecular alignment in the intermediate state.4. Ionization of organometallic compound by laser irradiation on a metal plate. Laser light from an <Nd^(2+)> : YAG laser (fundamental, 2nd, 3rd and 4th harmonics) was focused on a metal plate. A molecular beam of organometallic compound was injected in the neighborhood of the plate. Mass analysis of the product showed the production of organometallic ions, along with the metal ions from the plate. The mechanism of production of organometallic ions was discussed.