All-optical field-free three-dimensional orientation of asymmetric-top molecules

Abstract

Orientation and alignment of molecules by ultrashort laser pulses is crucial for a variety of applications and has long been of interest in physics and chemistry, with the special emphasis on stereodynamics in chemical reactions and molecular orbitals imaging. As compared to the laser-induced molecular alignment, which has been extensively studied and demonstrated, achieving molecular orientation is a much more challenging task, especially in the case of asymmetric-top molecules. Here, we report the experimental demonstration of all-optical field-free three-dimensional orientation of asymmetric-top molecules by means of phase-locked cross-polarized two-color laser pulse. This approach is based on nonlinear optical mixing process caused by the off-diagonal elements of the molecular hyperpolarizability tensor. It is demonstrated on SO2 molecules and is applicable to a variety of complex nonlinear molecules.

Observation of persistent orientation of chiral molecules by a laser field with twisted polarization

“…Laser-induced molecular orientation is a more challenging task; however, several techniques have been suggested and demonstrated for impulsive orientation of linear and even asymmetric top molecules under field-free condition (see, e.g. (7 ), and references therein).…”

Spatiotemporal rotational dynamics of laser-driven molecules

“…A fundamentally new aspect of field free orientation initiated by fields with twisted polarization was discovered 66,122,145 -the orientation does not return to zero shortly after the end of the excitation but persists over time exceeding the time scale of the excitation pulses by several orders of magnitude. In all the previously known approaches to impulsive orientation of nonchiral molecules, including techniques using single-cycle THz pulses, 39,45,[111][112][113][114]119 alone or in combination with optical pulses, [116][117][118] or two-color laser fields, [44][45][46][47][48][49][50][51]146 the orientation is short-lived and disappears rapidly after the end of the excitation pulses. Transient revival spikes may appear at longer times, however, they ride on a zero baseline and their time average is exactly zero.…”

“…Here we review the first experimental demonstration of alloptical field-free orientation of asymmetric-top SO 2 molecules using phase-locked orthogonal two-color (OTC) laser fields, 146 consisting of FW and its temporally overlapped SH. The FW aligns the MPA of the molecule along the polarization direction, whereas the two fields together orient the molecules via the offdiagonal components of the molecular hyperpolarizability tensor.…”

Direct imaging of molecular rotation with high-order-harmonic generation

“…In the present work, we demonstrate the application of machine learning in HHS to probe molecular rotational dynamics with high resolution and fidelity. Molecular rotational control by coherently manipulating the rota- tional wave packet (RWP) has been proved an efficient way to connect the molecular and laboratory frames [40][41][42][43][44], which is significant for molecular structure imaging [25][26][27] and chemical reaction steering [22,45]. In experiment, the molecular frame dynamics is usually convolved with the rotational distribution of molecules in laboratory.…”