Unraveling photodissociation dynamics by sub-femtosecond ultraviolet pulses: insights into fragmental kinetics and carrier-envelope phase characterization

Abstract

The duration of laser pulses and the carrier-envelope phase (CEP) play a crucial role in shaping kinetic energy release (KER) spectra. In this study, we performed theoretical calculations on pulse duration-dependent KER spectra, ranging from hundreds to sub-femtoseconds, focusing on the $\rm{MgH^+}$ scenario. Our findings reveal a distinct shift in KER peaks from sub-cycle pulses, deviating from the resonance energy. Utilizing two-level perturbation theory, we identify that this shift is attributable to the energy-dependent transition matrix elements. Moreover, our investigation uncovers a notable CEP effect in KER from sub-cycle pulses, arising from interference between counter-rotating and rotating terms within a single ultraviolet (UV) photon transition. To leverage this insight, we propose a novel pump-probe methodology for precise CEP characterization of ultra-short laser pulses. We hope this method would promise advancements in understanding and manipulating ultrafast processes.

Vibronic Correlations in Molecular Strong-Field Dynamics

“…Intuitively, one would think that a CEP-dependence is directly related to the laser pulse duration. Indeed, one expects the CEP dependence to be averaged out for longer pulses. − However, it unexpectedly turns out that the ϕ CE dependence gets even more pronounced when the pulse duration increases, as clearly seen in Figure . The effects of the vibronic correlations rather seem to build up during the laser pulse, requiring longer pulses to have a substantial influence.…”