Towards universal detection with 213 nm for velocity map imaging

• Published in: Journal of chemical sciences (Bangalore, India) India), 2023-08, Vol.135 (3), Article 92
• Main Authors: Singh, Sumitra, Kawade, Monali, Chowdhury, Prahlad Roy, Patwari, G Naresh
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Regular Article
• ISSN: 0973-7103; 0973-7103
• DOI: 10.1007/s12039-023-02211-z

The velocity map imaging of the methyl radical formed by 266 nm photolysis of methyl iodide using the 213 nm non-resonant multi-photon ionization (NRMPI) method is presented. Comparison of the NRMPI method with the well-known 2+1 resonance enhanced multi-photon ionization (REMPI) method at 333.45 nm, which selectively probes the Q-branch of band-origin transition of the methyl radical, indicates that the NRMPI method yields a significantly higher I/I* branching, 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 CH 3 +I dissociation channel. Further, photodissociation of the organic molecules yielding photofragments such as NO, CF 3 , CO, and several others could be detected and imaged using a 213 nm probe laser. Thus, results obtained in the present work signify that a 213 nm light source, which is easily available as the fifth harmonic of Nd:YAG laser, can be used as an alternative and efficient probe to investigate photodissociation dynamics of polyatomic molecules. Graphical abstract The utility of 213 nm (fifth harmonic of the Nd:YAG laser) as a universal ionization source in the imaging of several photodissociation products such as NO, CH 3 , CF 3 , CO, and other molecular fragments either via REMPI or NRMPI ionization methods is explored.