Impulsive Collision Dynamics of CO Super Rotors from an Optical Centrifuge

Murray, Matthew J.; Ogden, Hannah M.; Toro, Carlos; Liu, Qingnan; Mullin, Amy S.

doi:10.1002/cphc.201600871

Cited by 12 publications

(11 citation statements)

References 33 publications

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“…Gases of superrotors have been already studied both theoretically and experimentally. They have unique kinetic and optical properties [21,22,23], demonstrate inhibited rotational relaxation rate [24,20,25,26,21,27,22], persistent optical anisotropy [21,22,28], and giant rotational Doppler shift [29,23,20]. Here we show, for the first time, that such a gas is extremely optically active, with a giant specific rotation power in a broad wavelength range.…”

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confidence: 76%

“…Equation (7) expresses the relation between the dispersion and the polarization drag, and allows assessment of the effect based on the known data regarding the refractive index of a gas of non-rotating molecules. In order to estimate the magnitude of the effect, we consider parameters typical for several published optical centrifuge setups spinning various linear molecules, like N 2 , O 2 , CO 2 or N 2 O [24,20,28,27]. Taking oxygen superrotors [20] as an example, we note that just after the end of the centrifugation pulse, the gas demonstrates linear birefringence because of the remnant alignment of the molecules that were trapped by the centrifuge field.…”

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confidence: 99%

“…At room temperature, the decay time of linear birefringence ranges from several tens of ps×atm (picosecond×atmosphere) for moderately high rotational excitation [32,33,34,35], to hundreds of ps×atm in fully developed superrotor regime [25]. This leads to a practical loss of the linear birefringence (when probing along the rotation axis) within about a nanosecond, well before the rotational energy decays [25,21,22,27]. From this moment onward, the gas is suitable for polarization rotation measurements.…”

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confidence: 99%

“…−1 • (dm) −1 , a value that, when realized, would exceed the results of the slow light experiment [10] by four orders of magnitude. The immunity of the superrotors to collisions [24,20,28,21,22,27] makes this effect stable and long lasting, allowing multiple passages of light through the superrotor area for even further increase of the observed polarization rotation angle.…”

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Giant polarization drag in a gas of molecular super-rotors

Steinitz

Averbukh

2020

Phys. Rev. A

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Experiments on light dragging in a moving medium laid the cornerstones of modern physics more than a century ago, and they still are in the focus of current research. When linearly polarized light is transmitted through a rotating dielectric, the polarization plane is slightly rotated -a phenomenon first studied by Fermi in 1923. For typical non-resonant dielectric materials, the measured polarization drag angle does not surpass several microradians. Here we show that this effect may be dramatically enhanced if the light is sent to a gas of fast unidirectionally spinning molecular superrotors. Several femtosecond-laser labs have already succeeded in optically creating such a medium. We show that the specific rotation power of the superrotor medium exceeds the values previously observed in mechanically rotated bulk optical specimens by many orders of magnitude. This nonreciprocal opto-mechanical phenomenon may open new avenues for ultra-fast control of the polarization state of light.Main text: Light propagating in a moving medium can be 'dragged' by it and change the speed depending on the medium motion. This was first discussed by Fresnel in 1818 when considering a hypothetical 'aether drag' [1], and studied experimentally by Fizeau [2] in a real moving dielectric medium-water flowing in the arms of an optical interferometer. In 1885 Thomson considered an electromagnetic wave traveling in a rotating aether [3], and argued that the light should experience a transverse drag leading to the rotation of the field polarization vector. While the Michelson-Morley experiment [4] essentially ruled out the notion of 'luminiferous aether', the problem of polarization drag in a real rotating matter was examined by Fermi [5], who considered it as a generalization of the Fizeau experiment. The phenomenon was then studied in depth theoretically [6,7,8], and was first observed experimentally by Jones [9] using a rotating glass rod. The observed polarization rotation angle (which is proportional to the angular velocity of the glass rotation, and to the time it takes the light to traverse the specimen) was very smallseveral microradians. Jones' experiment approached the mechanical and material strength limits, and for more than 30 years no other research managed to exceed or reproduce his result. A remarkable advance was introduced in 2011 when the rotary polarization drag was enhanced by about four orders of magnitude by using near-resonant slow-light in a rotating solid ruby rod [10]. Recently it was shown that the rotary polarization drag takes place on astronomical scale in the magnetosphere of rotating pulsars, offering a unique means to determine the rotation direction of pulsars [11]. The effect is especially important since it is nonreciprocal, i. e., creates asymmetric wave transmission between two locations.Here we propose an alternative system for creating rotational polarization drag at unprecedentedly 1 high specific rotation level -four orders of magnitude higher than in the above record slow-light experiment [10], a...

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Giant polarization drag in a gas of molecular super-rotors

Steinitz

Averbukh

2020

Phys. Rev. A

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“…Gases of unidirectionally rotating superrotors have been studied both theoretically and experimentally. They have many unique optical and kinetic properties; most relevant to this study are the rotational Doppler shift [24,27,28] and inhibited rotational relaxation rate [24,[29][30][31][32][33][34][35].…”

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Rotation of polarization of light propagating through a gas of molecular super-rotors

Tutunnikov,

Steinitz,

Gershnabel

et al. 2021

Preprint

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We present a detailed theoretical and experimental study of the rotation of the plane of polarization of light traveling through a gas of fast-spinning molecules. This effect is similar to the polarization drag phenomenon predicted by Fermi a century ago and it is a mechanical analog of the Faraday effect. In our experiments, molecules were spun up by an optical centrifuge and brought to the super-rotor state that retains its rotation for a relatively long time. Polarizability properties of fast-rotating molecules were analyzed considering the rotational Doppler effect and Coriolis forces. We used molecular dynamics simulations to account for intermolecular collisions. We found, both experimentally and theoretically, a nontrivial nonmonotonic time dependence of the polarization rotation angle. This time dependence reflects transfer of the angular momentum from rotating molecules to the macroscopic gas flow, which may lead to the birth of gas vortices. Moreover, we show that the long-term behavior of the polarization rotation is sensitive to the details of the intermolecular potential. Thus, the polarization drag effect appears as a novel diagnostic tool for the characterization of intermolecular interaction potentials and studies of collisional processes in gases.

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Anomalous Intensities in the 2+1 REMPI Spectrum of the E ¹Π–X ¹Σ⁺ Transition of CO

et al. 2019

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We report on one-color experiments near 214 nm involving the photodissociation of jet-cooled OCS to produce high rotational states (40 < J < 80) of CO (X 1Σ+, v = 0, 1) which were then ionized by 2+1 resonance-enhanced multiphoton ionization via the E 1Π state. The nominally forbidden Q-branch of the two-photon E 1Π–X 1Σ+ transition is observed with intensity comparable to the allowed R-branch. The bright character of the high-J Q-branch lines can be described quantitatively as intensity borrowing due to mixing of the E 1Π and C 1Σ+ states, using J-dependent mixing coefficients extrapolated from the observed Λ-doubling in the lower rotational levels of the E state. In addition to the significant enhancement of Q-branch intensities above the values predicted by conventional two-photon line strengths for a 1Π–1Σ+ transition, the high-J lines of the R- and P-branches appear to be suppressed in intensity by approximately a factor of 3 compared to the unperturbed low-J line strengths, most likely due to perturbations associated with a 1Σ– state. The E-state rotational term values for J < 80, v = 0 derived from the present spectra agree within our measurement and calibration uncertainties with the extrapolations based on the molecular constants previously derived from rotational levels with J < 50. The E–X transition is attractive for future application to photodissociation dynamics and rotational polarization measurements of CO photofragments, with convenient access to state-selective probing on multiple rotational branches, which exhibit different sensitivity to fragment alignment.

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Impulsive Collision Dynamics of CO Super Rotors from an Optical Centrifuge

Cited by 12 publications

References 33 publications

Giant polarization drag in a gas of molecular super-rotors

Giant polarization drag in a gas of molecular super-rotors

Rotation of polarization of light propagating through a gas of molecular super-rotors

Anomalous Intensities in the 2+1 REMPI Spectrum of the E ¹Π–X ¹Σ⁺ Transition of CO

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Impulsive Collision Dynamics of CO Super Rotors from an Optical Centrifuge

Cited by 12 publications

References 33 publications

Giant polarization drag in a gas of molecular super-rotors

Giant polarization drag in a gas of molecular super-rotors

Rotation of polarization of light propagating through a gas of molecular super-rotors

Anomalous Intensities in the 2+1 REMPI Spectrum of the E 1Π–X 1Σ+ Transition of CO

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Anomalous Intensities in the 2+1 REMPI Spectrum of the E ¹Π–X ¹Σ⁺ Transition of CO