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Laser-induced dynamics of molecules with strong nuclear quadrupole coupling
摘要： We present a general variational approach for computing the laser-induced rovibrational dynamics of molecules, taking into account the hyperfine effects of the nuclear quadrupole coupling. The method combines the general variational approach TROVE (Theoretical Ro-Vibrational Energies), which provides accurate rovibrational hyperfine energies and wavefunctions for arbitrary molecules, with the variational method RichMol, designed for generalized simulations of the rovibrational dynamics in the presence of external electric fields. We investigate the effect of the nuclear quadrupole coupling on the short-pulse laser alignment of a prototypical molecule CFClBrI, which contains nuclei with large quadrupole constants. The influence of the nuclear quadrupole interactions on the postpulse molecular dynamics is negligible at early times, for the first several revivals; however, at longer time scales, the effect is entirely detrimental and strongly depends on the laser intensity. This effect can be explained by dephasing in the laser-excited rotational wavepacket due to irregular spacings between the hyperfine-split nuclear spin states across different rotational hyperfine bands.
关键词： laser-induced dynamics,nuclear quadrupole coupling,rovibrational dynamics,hyperfine effects,molecular alignment
更新于2025-09-12 10:27:22
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Controlling polarization of high-order harmonic generation by molecular alignment in a bicircular laser field
摘要： The polarization of high-order harmonic generation in H2+ driven by a counterrotating bichromatic ω/3ω circularly polarized laser field is investigated theoretically. The elliptically polarized harmonics are characterized by ellipticity and rotation angle, where the latter is expanded to [?π /2, π /2] by an optimized definition. We find a critical alignment angle where the ellipticity of high-energy harmonics is almost the same, so an attosecond pulse train with a high degree of polarization can be synthesized. In addition, we find that the rotation angle is always different from the alignment angle by 90? with a small deflection. Thus, we propose a scheme to control the harmonic polarization state by the molecular alignment angle.
关键词： molecular alignment,attosecond pulse,high-order harmonic generation,polarization,bicircular laser field
更新于2025-09-11 14:15:04
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Symmetry of molecular Rydberg states revealed by XUV transient absorption spectroscopy
摘要： Transient absorption spectroscopy is utilized extensively for measurements of bound- and quasibound-state dynamics of atoms and molecules. The extension of this technique into the extreme ultraviolet (XUV) region with attosecond pulses has the potential to attain unprecedented time resolution. Here we apply this technique to aligned-in-space molecules. The XUV pulses are much shorter than the time during which the molecules remain aligned, typically <100 fs. However, transient absorption is not an instantaneous probe, because long-lived coherences re-emit for picoseconds to nanoseconds. Due to dephasing of the rotational wavepacket, it is not clear if these coherences will be evident in the absorption spectrum, and whether the properties of the initial excitations will be preserved. We studied Rydberg states of N2 and O2 from 12 to 23 eV. We were able to determine the polarization direction of the electronic transitions, and hence identify the symmetry of the final states.
关键词： transient absorption spectroscopy,extreme ultraviolet,attosecond pulses,molecular alignment,Rydberg states
更新于2025-09-11 14:15:04