Work

Isotope Effect on the Few-Femtosecond Relaxation Dynamics of the Ethylene Cation

Year: 2025

Type: article

Abstract: Few-femtosecond extreme-ultraviolet (EUV) pulses with tunable energy are employed to initiate the Jahn–Teller structural rearrangement in the ethylene cation. We report on a combined experimental and theoretical investigation of an unusual isotope effect on the low-energy competing H/D-loss and H 2 /D 2 -loss channels observed in the ultrafast dynamics induced by an EUV-pump pulse and probed by an infrared (IR) pulse. The relative production yields of C 2 D 4 +, C 2 D 3 +, and C 2 D 2 + exhibit pronounced oscillations with a period of ∼50 fs as a function of the pump–probe delay, while the oscillatory patterns are less pronounced for C 2 H 4 + . By using surface hopping to model the nonadiabatic dynamics in the four lowest electronic states of the cation, we show that the enhanced oscillations in deuterated fragment yields arise from a synergy between the isotope effects on the wave packet relaxation through the network of conical intersections and on the vibrational frequencies of the cation.

Source: The Journal of Physical Chemistry A

DOI: 10.1021/acs.jpca.5c01020