Publications

1994
Uri Banin, Allon Bartana, Sanford Ruhman, and Ronnie Kosloff. 1994. “Impulsive excitation of coherent vibrational motion ground surface dynamics induced by intense short pulses.” The Journal of chemical physics, 101, 10, Pp. 8461-8481. Publisher's Version Abstract

A framework for understanding impulsively photoinduced vibrational coherent motion on the ground electronic surface is presented. In particular strong resonant excitation to a directly dissociative electronic surface is considered. Three distinct approaches are employed. A two surface Fourier wavepacket method explicitly including the field explores this process in isolated molecules. A coordinate dependent two‐level system is employed to develop a novel analytical approximation to the photoinduced quantum dynamics. The negligible computational requirements make it a powerful interactive tool for reconstructing the impulsive photoexcitation stage. Its analytical nature provides closed form expressions for the photoinduced changes in the material. Finally the full simulation of the process including the solvent effects is carried out by a numerical propagation of the density operator. In all three techniques the excitation field is treated to all orders, allowing an analysis of current experiments using strong fields, resulting in substantial photoconversion. The emerging picture is that the impulsive excitation carves a coherent dynamical ‘‘hole’’ out of the ground surface density. A rigorous definition of the dynamical ‘‘hole’’ is constructed and used to define a measure of its coherence. In particular all photoinduced time dependence in the system can be directly related to the dynamical ‘‘hole.’’ All three techniques are used to simulate the pump probe experiment on the symmetric stretch mode of I3, including electronic and vibrational dephasing.

Uri Banin, Allon Bartana, Sanford Ruhman, and Ronnie Kosloff. 1994. “Impulsive excitation of coherent vibrational motion ground surface dynamics induced by intense short pulses.” The Journal of chemical physics, 101, 10, Pp. 8461-8481. Publisher's Version Abstract

A framework for understanding impulsively photoinduced vibrational coherent motion on the ground electronic surface is presented. In particular strong resonant excitation to a directly dissociative electronic surface is considered. Three distinct approaches are employed. A two surface Fourier wavepacket method explicitly including the field explores this process in isolated molecules. A coordinate dependent two‐level system is employed to develop a novel analytical approximation to the photoinduced quantum dynamics. The negligible computational requirements make it a powerful interactive tool for reconstructing the impulsive photoexcitation stage. Its analytical nature provides closed form expressions for the photoinduced changes in the material. Finally the full simulation of the process including the solvent effects is carried out by a numerical propagation of the density operator. In all three techniques the excitation field is treated to all orders, allowing an analysis of current experiments using strong fields, resulting in substantial photoconversion. The emerging picture is that the impulsive excitation carves a coherent dynamical ‘‘hole’’ out of the ground surface density. A rigorous definition of the dynamical ‘‘hole’’ is constructed and used to define a measure of its coherence. In particular all photoinduced time dependence in the system can be directly related to the dynamical ‘‘hole.’’ All three techniques are used to simulate the pump probe experiment on the symmetric stretch mode of I3, including electronic and vibrational dephasing.

Allon Bartana, Uri Banin, Sanford Ruhman, and Ronnie Kosloff. 1994. “Intensity effects on impulsive excitation of ground surface coherent vibrational motion: A ‘V’jump simulation.” Chemical physics letters, 229, 3, Pp. 211-217. Publisher's Version Abstract

Control of coherent ground surface dynamics is achieved by varying the intensity of a resonant ultrafast pump pulse. This pulse cycles amplitude between the ground and excited electronic surfaces resulting in a momentum kick and a coordinate dependent loss of amplitude, creating a nonstationary vibrational distribution: the ‘V’ jump. A qualitative change in composition occurs for intensities above π pulse conditions. The induced dynamics is observed by a delayed pulse which is dispersed and analyzed against time or as a two-dimensional frequency plot. Such an analysis makes it possible to distinguish the contributions of high vibrational harmonics to the dynamics.