Coherent control of radiationless transitions: Simultaneous excitation and decay of overlapping resonances

Abstract

We develop a simple analytical theory for the study of coherent control of radiationless transitions, and in particular, internal conversion leading to dissociation, in molecules possessing overlapping resonances. The method is applied to a model diatomic system. In contrast to previous studies, we consider here the control of a molecule that is allowed to decay during and after the preparation process. We use this theory to derive the shape of the laser pulse that creates the specific excited wave packet that best enhances or suppresses the radiationless transitions process. The results show the importance of resonance overlap in the molecule in order to achieve efficient coherent control over radiationless transitions via laser excitation. Specifically, resonance overlap is proven to be crucial in order to alter interference contributions to the controlled observable, and hence to achieve efficient coherent control by varying the phase of the laser field.

Coherent Control of Photofragment Distributions Using Laser Phase Modulation in the Weak-Field Limit

“…35−38 Recent work on coherent control has discussed the significant role of interference between overlapping resonances in relation to the population dynamics of electronically excited molecular states. 39,40 As we will show in the following, pure phase modulation of the laser pulse can lead to different postpulse distributions of the final vibrational states v f when the dynamics involve interfering overlapping resonances.…”

Coherent phase control of internal conversion in pyrazine

“…[48,49] The overlapping resonance mechanism [9,50,51] of Brumer, Shapiro, and coworkers predicted suppression of IC for up to 100 fs, although longer control periods may be possible by this mechanism.…”

Selective coherent control of the lifetime of a resonance state with laser pulses

“…It is also noted that the enhancement of the ability of control when the density of overlapping resonances increases has been shown and discussed as well in the context of control of the decay of the whole coherent superposition of resonances prepared. 29,30 Thus, investigating in detail how the degree of control of a single resonance lifetime can be increased when we change to a denser overlapping regime is a most interesting issue, and is the main goal of the present work.…”

“…26,27 Among the schemes proposed, one is based on controlling the quantum interference that occurs between overlapping resonances of the system populated by a coherent superposition created by a laser pulse, by varying the relative amplitude of the resonances. [28][29][30] An extensive discussion and an analytical treatment of the preparation and decay evolution of a superposition of overlapping resonances are presented in Ref. 28(a).…”