Probing nonadiabatic molecular alignment by spectral modulation

Abstract

We investigated molecular alignment wakes of femtosecond laser pulses. Evolution of nonadiabatic molecular alignment in nitrogen gas has been measured via its nonlinear interaction effects with a variably delayed probe pulse. The induced rotational wave packet was mapped as a function of the angular difference between polarization directions of femtosecond pump and probe pulses as well as their relative delay and the plot of the variations of the rotational wave packet, i.e. "quantum carpet", was found to be in good agreement with the calculated angular and temporal dependencies of molecular alignment parameter.

Control of laser-induced nonadiabatic molecular alignment in dissipative media

“…The standard version of the setup in Refs. [22,32], in which the pump and probe beams propagate collinearly and are discriminated spectrally rather than spatially, was used successfully for measurements at room temperature. Aside from easier adjustment, the setup has the additional advantage of providing a large interaction volume even for lenses with relatively short focal length.…”

“…Femtosecond laser systems with advanced technology enable one to align molecules and observe the molecular dynamics by using a pump-probe technique [9]. Here an initial pump pulse induces the formation of a dynamically anisotropic medium that will dephase and rephase in time, and after that simultaneous variations in the interaction between such a medium and a probe pulse can be detected through different processes such as ionization [1,[10][11][12], fragmentation [13,14], and high harmonic generation [6,[15][16][17][18] or by spatial and spectral modulation of the probe pulse [19][20][21][22][23].…”

Control of Femtosecond Filamentation by Means of the Alignment of Gas Molecules by Short-Wavelength Infrared Laser Pulses

“…However, the parameters of the experiments in these works (intensity of the laser pulse, focusing, the length of the filament, the pressure and type of the gas) were significantly different. Furthermore, as shown below, the methods used in [17][18][19][20][21][22] to detect the dynamics of the refractive index caused by the alignment of molecules were inappropriate and gave contradictory results.…”

Controlled formation of femtosecond laser-induced filaments in water

“…The critical power for self-focusing for an elliptical beam was found to be greater than a beam with cylindrical symmetry, and the role of the elliptical intensity distribution was discussed in details [14][15][16][17][18]. Studies also show that controlling and organizing filament formations are possible by inserting slits and meshes into the beam path of an intense laser pulse [19], creating Fresnel diffraction from a circular aperture [20], applying amplitude [21,22] and phase [23,24] modulation of the beam field, combining the phase plates [25], producing high order Hermite Gaussian beams [26] and Bessel Gaussian beams [27], probing nonlinear molecular alignment [28][29][30] and crossing two femtosecond laser beams [31] etc.…”