| Popis: |
The velocity map imaging of the methyl radical formed by 266 nm photolysis of methyl iodide using 213 nm non-resonant multi-photon ionization (NRMPI) method. Comparison of the NRMPI method with the well-known (2+1) resonance multi-photon ionization (REMPI) method at 333.45 nm, which selectively probes Q-branch of band-origin transition of the methyl radical, indicates that the NRMPI method yields a significantly higher I/I* branching ratio in comparison to the REMPI method, even though the velocity map images of both the methods are qualitatively similar. The higher I/I* branching ratio obtained in the NRMPI method is attributed to the non-resonant ionization of higher quanta states of the umbrella bending mode along with higher rotational states of the methyl fragment in the CH3+I dissociation channel. Thus, results obtained in the present work signify that a 213 nm excitation source, which is easily available as the fifth harmonic of Nd:YAG laser, can be used as an alternative and efficient probe to investigate photo-dissociation dynamics of polyatomic molecules. |
