Strong-field ionization of polyatomic molecules: ultrafast H atom migration and bond formation in the photodissociation of CH3OH

Abstract

Strong-field ionization induces various complex phenomena like bond breaking, intramolecular hydrogen migration, and bond association in polyatomic molecules. The H-atom migration and bond formation in CH₃OH induced by intense femtosecond laser pulses are investigated using a Velocity Map Imaging (VMI) spectrometer. Various laser parameters like intensity (1.5 × 10¹³ W cm⁻²–12.5 × 10¹³ W cm⁻²), pulse duration (29 fs and 195 fs), wavelength (800 nm and 1300 nm), and polarization (linear and circular) can serve as a quantum control for hydrogen migration and the yield of H_n⁺ (n = 1–3) ions which have been observed in this study. Further, in order to understand the ejection mechanism of the hydrogen molecular ions H₂⁺ and H₃⁺ from singly-ionized CH₃OH, quantum chemical calculations were employed. The dissociation processes of CH₃OH⁺ occurring by four dissociative channels to form CHO⁺ + H₃, H₃⁺ + CHO, CH₂⁺ + H₂O, and H₂O⁺ + CH₂ are studied. Using the combined approach of experiments and theory, we have successfully explained the mechanism of intramolecular hydrogen migration and predicted the dissociative channels of singly-ionized CH₃OH.