Ultrafast Angular Momentum Orientation by Linearly Polarized Laser Fields

Abstract

We theoretically show and experimentally verify that a pair of linearly polarized intense femtosecond pulses can create molecular ensembles with oriented rotational angular momentum on an ultrafast (approximately ps) time scale, when the delay and the mutual polarization between them are appropriately arranged. An asymmetric distribution for +M and -M sublevels relies on quantum interference between rotational wave packets created in stimulated Raman excitation by the first and second pulses. The present approach provides spatiotemporally propagating ensembles, of which the classical perspective is molecules rotating in a clockwise or counterclockwise direction.

Controlling molecular scattering by laser-induced field-free alignment

“…Narrowing the distribution of the scattering angles may substantially increase the efficiency of separation of multi-component beams, especially when the prealignment is applied selectively to certain molecular species, such as isotopes [25], or nuclear spin isomers [26,27]. More complicated techniques for pre-shaping the molecular angular distribution may be considered, such as confining molecular rotation to a certain plane by using the "optical molecular centrifuge" approach [28], double-pulse ignited "molecular propeller" [29][30][31][32][33], or planar alignment by perpendicularly polarized laser pulses [34]. In this case, a narrow angular peak is expected in molecular scattering, whose position is controllable by inclination of the plane of rotation with respect to the deflecting field [35].…”

Modifying molecular scattering from rough solid surfaces using ultrashort laser pulses

“…This can be also seen from the second term on the right of Eq. (34). On the other hand, the friction force acts always in the same direction on the molecules falling on the surface from the left (negative incident angles).…”

“…Before hitting the surface, the molecules are illuminated by two consecutive laser pulses, following the scheme introduced in [33], and experimentally realized in [34]. See Section III for the rotational velocity change caused by a single laser pulse.…”

Unidirectional Rotation of Molecules Measured by the Rotational Doppler Effect

“…In Ref. [3], a method of inducing field-free unidirectional molecular rotation (UDR) was suggested, which was then demonstrated in [4], and further extended in [5]. In the present paper, we use the RDS phenomenon to detect and quantify the field-free molecular UDR.…”