A simulation of ultrafast state-selective IR-laser-controlled isomerization of hydrogen cyanide based on global 3D ab initio potential and dipole surfaces

• Published in: Chemical physics Vol. 217; no. 2; pp. 375 - 388
• Main Authors: Jakubetz, Werner, Lan, Boon Leong
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-05-1997
• ISSN: 0301-0104
• DOI: 10.1016/S0301-0104(97)00056-6

An ultrafast state-selective laser-controlled pump-dump scheme proceeding in the electronic ground state is simulated for HCN → HNC isomerization. The simulation is based on global 3D ab initio electronic ground state potential and dipole surfaces. The dipole surface obtained as part of the present work is a fit to 2010 single-reference AQCC data points. Isomerization dynamics including all three vibrational degrees of freedom is treated within the
J = 0 vibrational manifold. Up to 550
J = 0 vibrational states previously reported by Bowman et al. [
J. Chem. Phys. 99 (1993) 308] are employed to obtain converged results. The laser polarization is fixed along the CN axis and molecular rotation is disregarded. Isomerization is initiated from HCN in its (
J = 0) vibrational ground sate, and control is exerted by a pulse sequence which splits the overall process into a sequence of state-specific sub-transitions. The intermediate states are chosen from a least-cost isomerization ladder obtained from an artificial intelligence algorithm, and include excited HCN bend states and a
delocalized vibrational state above the isomerization barrier. We demonstrate that the molecule can be prepared in a specified HNC bend state with high overall selectivity (> 92%) and without concomitant ionization or dissociation, on a picosecond timescale using 4 or 5 sequential mid-infrared Gaussian pulses.