arXiv subjects

Sharly Fleischer

Publications and source records attributed to Sharly Fleischer.

23 records · Page 2Linked to original sources

arXiv2015

From populations to coherences and back again: a new insight about rotating dipoles

The process in which light is absorbed by an ensemble of molecules obeys the fundamental law of conservation of energy - the energy removed from the light resides in the molecular degrees of freedom. In the process of coherent emission from excited molecules known as free-induction decay (FID), spectroscopic measurements of the emitted radiation are often conducted in order to gain insight into molecular structure and behavior. However, the direct influence of the FID emission on its molecular source is not measured directly. In this work we present experimental evidence from the molecular rotor perspective of the consequences of terahertz-frequency FID emission from rotationally excited molecules. We show that when gas phase molecules transiently orient under field-free conditions, the energy radiated via FID is manifest as an abrupt reduction in excited rotational populations. The connection between coherent FID emission and stored energy leaves a particularly distinct signature in our measurements, but the results are generalizable throughout coherent spectroscopy and coherent control.

physics.atom-ph↗

arXiv2011

Molecular Orientation by Intense Single Cycle THz Pulses

Intense single-cycle THz pulses resonantly interacting with molecular rotations are shown to induce significant field-free orientation under ambient conditions. We calculate and measure the angular distribution associated with THz-driven rotational motion and correlate the THz-induced orientation and alignment in an OCS gas sample.

physics.chem-ph↗

arXiv2009

Controlling the sense of molecular rotation

We introduce a new scheme for controlling the sense of molecular rotation. By varying the polarization and the delay between two ultrashort laser pulses, we induce unidirectional molecular rotation, thereby forcing the molecules to rotate clockwise/counterclockwise under field-free conditions. We show that unidirectionally rotating molecules are confined to the plane defined by the two polarization vectors of the pulses, which leads to a permanent anisotropy in the molecular angular distribution. The latter may be useful for controlling collisional cross-sections and optical and kinetic processes in molecular gases. We discuss the application of this control scheme to individual components within a molecular mixture in a selective manner.

quant-ph↗

arXiv2007

Selective Rotational Excitation of Molecular Isotopes and Nuclear Spin Isomers

Following excitation by a strong ultra-short laser pulse, molecules develop coordinated rotational motion, exhibiting transient alignment along the direction of the laser electric field, followed by periodic full and fractional revivals that depend on the molecular rotational constants. In mixtures, the different species undergo similar rotational dynamics, all starting together but evolving differently with each demonstrating its own periodic revival cycles. For a bimolecular mixture of linear molecules, at predetermined times, one species may attain a maximally aligned state while the other is anti-aligned (i.e. molecular axes are confined in a plane perpendicular to the laser electric field direction). By a properly timed second laser pulse, the rotational excitation of the undesired species may be almost completely removed leaving only the desired species to rotate and periodically realign, thus facilitating further selective manipulations by polarized light. In this paper, such double excitation schemes are demonstrated for mixtures of molecular isotopes (isotopologues) and for nuclear spin isomers.

quant-ph↗

arXiv2006

Rotational Control and Selective Isotope Alignment by Ultrashort Pulses

Strong ultrashort laser pulses give rise to prompt molecular alignment followed by full, half and quarter quantum revivals of the rotational wave packets. In Four Wave Mixing (FWM) experiments, we make use of the long succession of repetitive alignment revivals to demonstrate isotope-selective alignment and time-resolved discrimination between different isotopic species. For two isotopes with a commensurate ratio of their moments of inertia, we observe constructive and destructive interferences of the FWM signals originating from different isotopes. Such destructive interference serves as an indication for distinct transient angular distributions of different isotopic species, paving the way to novel time-resolved analytic techniques, as well as to robust methods for isotope separation. When two pulses are used, enhancement or reduction of the degree of rotational excitation and of the corresponding molecular alignment is observed, depending on the delay between pulses. We implement the double pulse excitation scheme in a binary isotopic mixture, enhancing the rotational excitation of one isotopic component while almost totally reducing the rotational excitation of the other.

quant-ph↗