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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi mathvariant="normal">M</mml:mi> <mml:mi mathvariant="normal">g</mml:mi> <mml:msup> <mml:mi mathvariant="normal">H</mml:mi> <mml:mo>+</mml:mo> </mml:msup> </mml:mrow> </mml:math> 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 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.

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