Orientation of Asymmetric Top Molecules in a Uniform Electric Field: Calculations for Species without Symmetry Axes

• DOI: 10.1021/jp993549x
• Publication Date: 2002-07-26T06:02:09Z
• Authors: Wei Kong; Jaap Bulthuis
• Keywords: Hamiltonian (control theory)

Calculations of orientation effects polar molecules in a uniform electric field are presented for the most general scenario, an asymmetric top molecule with permanent dipole not parallel to principal axis. In addition details calculation procedure, including matrix elements Hamiltonian, three different treatments population distribution Stark levels discussed. The adiabatic approach assumes noncrossing rule all energy as increases, nonadiabatic searches level similar wave function under field-free conditions find field, and thermal levels. Among these, results highest degree orientation, high fields, it shows best agreement available experimental data terms polarization ratios (the overall excitation probabilities two perpendicular directions laser). By use cytosine at rotational temperature 5 K adenine 2 model compounds, suggests that 50 kV/cm, more than 30% should be confined within 45° cone surrounding direction if transition is dipole, probability can enhanced by 50% when laser perpendicular, rather parallel, field. calculations yield functions both predicting weaker calculation. According comparisons spectroscopic between experiment using π* ← n pyrimidine, however, agree spectra. Further evidence higher quality spectra needed conclusive statement. Orientation particularly suitable studies large systems small constants: effect proven determined size essentially independent molecular frame. For molecules, this type or unfavorable, resulting sensitive parameters, such constants,