Quantum Control of Molecular Gas Hydrodynamics

Zahedpour, S.; Wahlstrand, J. K.; Milchberg, H. M.

doi:10.1103/physrevlett.112.143601

Cited by 49 publications

(54 citation statements)

References 32 publications

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“…Intense ultrashort laser pulses can deposit energy in a transparent gas medium either by ionizing [1,2] or spinning up [3,4] its molecular constituents. Heating of the gas is followed by the formation of an acoustic wave [5][6][7][8] which leaves behind a long-lived low-density depression channel [9].…”

Section: Introductionmentioning

confidence: 99%

“…Heating of the gas is followed by the formation of an acoustic wave [5][6][7][8] which leaves behind a long-lived low-density depression channel [9]. Laser-induced sound emission is key to photoacoustic spectroscopy [10][11][12], whereas laser control of the gas density proved valuable for generating [13,14] and even controlling [4] wave-guiding channels in ambient air. Because ionization-free delivery of energy by means of rotational excitation does not inhibit coherent light propagation through the heated gas, it has the potential of producing longer wave guides, e.g., if executed inside ionization-free filaments [15].…”

Section: Introductionmentioning

confidence: 99%

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From Gyroscopic to Thermal Motion: A Crossover in the Dynamics of Molecular Superrotors

et al. 2015

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Localized heating of a gas by intense laser pulses leads to interesting acoustic, hydrodynamic, and optical effects with numerous applications in science and technology, including controlled wave guiding and remote atmosphere sensing. Rotational excitation of molecules can serve as the energy source for raising the gas temperature. Here, we study the dynamics of energy transfer from the molecular rotation to heat. By optically imaging a cloud of molecular superrotors, created with an optical centrifuge, we experimentally identify two separate and qualitatively different stages of its evolution. The first nonequilibrium "gyroscopic" stage is characterized by the modified optical properties of the centrifuged gas-its refractive index and optical birefringence, owing to the ultrafast directional molecular rotation, which survives tens of collisions. The loss of rotational directionality is found to overlap with the release of rotational energy to heat, which triggers the second stage of thermal expansion. The crossover between anisotropic rotational and isotropic thermal regimes is in agreement with recent theoretical predictions and our hydrodynamic calculations.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

From Gyroscopic to Thermal Motion: A Crossover in the Dynamics of Molecular Superrotors

et al. 2015

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“…According to the theory of laserinduced pressure waves in dense media [22], as well as numerical simulations of hydrodynamic expansion [7], the sound wave amplitude is expected to scale linearly with the amount of laser energy deposited in the sample. In the case of an impulsive rotational excitation, most of the energy is transferred via a single two-photon Raman transition, suggesting a quadratic dependence on the pulse energy [4], which has been recently verified experimentally [6,11]. In contrast, an adiabatic excitation by the centrifuge involves multiple transitions up RAMAN: One of the spectra from Sep26a sound data.…”

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confidence: 99%

“…Nonlinear change of refractive index gives rise to filamentation (recent reviews of this broad topic can be found in [1,2]), whereas spatially localized heating results in the formation of acoustic waves [3][4][5][6][7][8] and long-lived gas density perturbations [9][10][11]. Photo-acoustic vibrational Raman spectroscopy has been successfully utilized for chemical detection and trace analysis [12,13].…”

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confidence: 99%

Sound emission from the gas of molecular superrotors

Milner¹,

Korobenko²,

Milner³

2015

Opt. Express

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We use an optical centrifuge to deposit a controllable amount of rotational energy into dense molecular ensembles. Subsequent rotation-translation energy transfer, mediated by thermal collisions, results in the localized heating of the gas and generates strong sound wave, clearly audible to the unaided ear. For the first time, the amplitude of the sound signal is analyzed as a function of the experimentally measured rotational energy. The proportionality between the two experimental observables confirms that rotational excitation is the main source of the detected sound wave. As virtually all molecules, including the main constituents of the atmosphere, are amenable to laser spinning by the centrifuge, we anticipate this work to stimulate further development in the area of photo-acoustic control and spectroscopy.

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“…Magnetic effects could further broaden the controllability provided by tunable rotational excitation, including control of molecular collisions [12,13] and scattering of molecules at gas-solid interfaces [14], molecular trajectories [15] and formation of gas vortices [16], optical [5,17] and acoustic [19,20] properties of a gas of rotating molecules.…”

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confidence: 99%

Dynamics of molecular superrotors in an external magnetic field

Korobenko

Milner

2015

J. Phys. B: At. Mol. Opt. Phys.

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We excite diatomic oxygen and nitrogen to high rotational states with an optical centrifuge and study their dynamics in external magnetic field. Ion imaging is employed to directly visualize, and follow in time, the rotation plane of molecular superrotors. The two different mechanisms of interaction between the magnetic field and the molecular angular momentum in paramagnetic oxygen and non-magnetic nitrogen lead to the qualitatively different behaviour. In nitrogen, we observe the precession of the molecular angular momentum around the field vector. In oxygen, strong spin-rotation coupling results in faster and richer dynamics, encompassing the splitting of the rotation plane in three separate components. As the centrifuged molecules evolve with no significant dispersion of the molecular wave function, the observed magnetic interaction presents an efficient mechanism for controlling the plane of molecular rotation. PACS numbers:Magnetic field is one of the most powerful tools for controlling atomic and molecular dynamics. Both translational and rotational degrees of freedom of molecules have been successfully manipulated via various types of magnetic interaction. Alignment of molecular axes has been accomplished by creating pendular states in paramagnetic molecules at low temperature [1,2]. Gyroscopic precession along the direction of the applied magnetic field has been suggested for non-magnetic molecules in dispersionless "cogwheel" states [3,4]. Spin-rotational coupling has been recently utilized for converting unidirectional molecular rotation into axial alignment, manifested through magneto-rotational optical birefringence under ambient conditions [5,6].Recent progress in creating and detecting unidirectional rotation of molecules [7][8][9][10][11]18] revived the interest in controlling molecular rotation with external magnetic fields. Magnetic effects could further broaden the controllability provided by tunable rotational excitation, including control of molecular collisions [12,13] and scattering of molecules at gas-solid interfaces [14], molecular trajectories [15] and formation of gas vortices [16], optical [5, 17] and acoustic [19,20] properties of a gas of rotating molecules.With the invention of the optical centrifuge technique [21,22], a very flexible control over the degree of rotational excitation became available. The technique proved capable of producing synchronously rotating molecules with narrow rotational state distribution in a wide variety of species up to extremely high angular frequencies [5,23]. However, the spatial orientation of the induced angular momentum is often defined by the propagation direction of the excitation laser beam, and is therefore not easy to manipulate.Here we demonstrate how an applied magnetic field can be used to rotate the plane of molecular rotation. The described method is applicable to a wide variety of molecules and relies on the coupling between the rotation of a molecule and its magnetic moment. An applied magnetic field causes this moment to precess, "...

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Quantum Control of Molecular Gas Hydrodynamics

Cited by 49 publications

References 32 publications

From Gyroscopic to Thermal Motion: A Crossover in the Dynamics of Molecular Superrotors

From Gyroscopic to Thermal Motion: A Crossover in the Dynamics of Molecular Superrotors

Sound emission from the gas of molecular superrotors

Dynamics of molecular superrotors in an external magnetic field

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