Non-adiabatic transition in C₂H₅OH⁺ on a light-dressed potential energy surface by ultrashort pump-and-probe laser pulses

We experimentally investigate how parameters of ultrashort laser pulses such as the pulse width and wavelength could induce changes in the dynamics of vibrational wave packets on the light-dressed-potential energy surface (LD-PES) of C₂H₅OH⁺ using a pump-and-probe pulse excitation scheme. The probability of non-adiabatic transition at 800 nm from the singly ionized ground state to the repulsive excited state leading to C-O bond breaking is enhanced when a probe laser pulse is delayed by ∼180 fs. At this pulse delay, on the other hand, C-C bond breaking is significantly suppressed. Therefore, the deformation of LD-PES is considered to change the direction of the wave packet traveling originally along the C-C stretching into the direction along the C-O stretching. This non-adiabatic transition leading to the redirection of the dissociating wave packet is found to occur more efficiently at the probe laser wavelengths at 400 nm than at 800 nm. The critical pulse delay is still ∼180 fs even at 400 nm.