Abstract
Molecules have long been known to align in moderately intense, far off-resonance laser fields with a large variety of applications in physics and optics. We illustrate and describe the physical origin of a previously unexplored phenomenon in the adiabatic alignment dynamics of molecules, which is fundamentally interesting and also has an important practical implication. Specifically, the intensity dependence of the degree of adiabatic alignment exhibits a threshold behavior, below which molecules are isotropically distributed rotationally and above which the alignment rapidly reaches a plateau. Furthermore, we show that both the intensity and the temperature dependencies of the alignment of all linear molecules exhibit universal curves and derive analytical forms to describe these dependencies. Finally, we illustrate that the alignment threshold occurs very generally at a lower intensity than the off-resonance ionization threshold, a numerical observation that is readily illustrated analytically. The threshold behavior is attributed to a tunneling mechanism that rapidly switches off at the threshold intensity, where tunneling between the potential wells corresponding to the two orientations of the aligned molecules becomes impossible. The universal threshold behavior of molecular alignment is a simple phenomenon, but one that was not realized before and can be readily tested experimentally.
Original language | English (US) |
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Article number | 183201 |
Journal | Physical review letters |
Volume | 129 |
Issue number | 18 |
DOIs | |
State | Published - Oct 28 2022 |
Funding
We thank the Department of Energy (Award No. DE-FG02-04ER15612/0013) for support of the research leading to this manuscript.
ASJC Scopus subject areas
- General Physics and Astronomy