Femtosecond XUV–IR induced photodynamics in the methyl iodide cation. (13th July 2021)

• Record Type: Journal Article
• Authors: Murillo-Sánchez, Marta L; Reitsma, Geert; Poullain, Sonia Marggi; Fernández-Milán, Pedro; González-Vázquez, Jesús; de Nalda, Rebeca; Martín, Fernando; Vrakking, Marc J J; Kornilov, Oleg; Bañares, Luis
• Is Part Of: New journal of physics. Volume 23:Number 7(2021)
• Publication Date: 2021-07-13
• Subjects: high harmonic generation -- XUV photoionization -- femtosecond dynamics -- time delay compensated monochromator; Physics -- Periodicals; Physics; Periodicals; 530.05
• DOI: 10.1088/1367-2630/ac0c9b
• Languages: English
• ISSNs: 1367-2630

Abstract

Abstract: The time-resolved photodynamics of the methyl iodide cation (CH3 I + ) are investigated by means of femtosecond XUV–IR pump–probe spectroscopy. A time-delay-compensated XUV monochromator is employed to isolate a specific harmonic, the 9th harmonic of the fundamental 800 nm (13.95 eV, 88.89 nm), which is used as a pump pulse to prepare the cation in several electronic states. A time-delayed IR probe pulse is used to probe the dissociative dynamics on the first excited A ̃ A 1 2 state potential energy surface. Photoelectrons and photofragment ions— C H 3 + and I + —are detected by velocity map imaging. The experimental results are complemented with high level ab initio calculations for the potential energy curves of the electronic states of CH3 I + as well as with full dimension on-the-fly trajectory calculations on the first electronically excited state A ̃ A 1 2, considering the presence of the IR pulse. The C H 3 + and I + pump–probe transients reflect the role of the IR pulse in controlling the photodynamics of CH3 I + in the A ̃ A 1 2 state, mainly through the coupling to the ground state X ̃ E 3 / 2, 1 / 2 2 and to the excited B ̃ E 2 state manifold. Oscillatory features are observed and attributed to a vibrational wave packet prepared in the A ̃ A 1 2 state. The IR probe pulse induces a coupling between electronic states leading to a slow depletion of C H 3 + fragments after the cation is transferred to the ground X ̃ E 3 / 2, 1 / 2 2 states and an enhancement of I + fragments by absorption of IR photons yielding dissociative photoionization.