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Arndt PT, Huennekens J, Packard C, Tran V, Carey J, Livingston R, Marcune VM, Rowe BA, Ng J, Qi J, Lyyra AM, Ahmed EH. The effect of collisions on the rotational angular momentum of diatomic molecules studied using polarized light. J Chem Phys 2020; 153:184310. [DOI: 10.1063/5.0024380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- P. T. Arndt
- Physics Department, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - J. Huennekens
- Physics Department, Lehigh University, Bethlehem, Pennsylvania 18015, USA
| | - C. Packard
- Physics Department, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - V. Tran
- Physics Department, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - J. Carey
- Physics Department, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - R. Livingston
- Physics Department, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - V. M. Marcune
- Physics Department, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - B. A. Rowe
- Physics Department, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - J. Ng
- Physics Department, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - J. Qi
- Department of Physics and Astronomy, Penn State University, Berks Campus, Reading, Pennsylvania 19610, USA
| | - A. M. Lyyra
- Physics Department, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - E. H. Ahmed
- Physics Department, Temple University, Philadelphia, Pennsylvania 19122, USA
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Price TJ, Hickman AP. Semiclassical analysis of jm → j'm' transitions in rotationally inelastic collisions in cell experiments. J Chem Phys 2018; 148:074105. [PMID: 29471636 DOI: 10.1063/1.4996877] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Recent quantum calculations of rotationally inelastic collisions of NaK (A1Σ+) with He or Ar in a cell experiment are analyzed using semiclassical approximations valid for large quantum numbers. The results suggest a physical interpretation of jm → j'm' transitions based on the vector model and lead to expressions that explicitly involve the initial and final polar angles of the angular momentum of the target molecule. The relation between the polar angle θ and the azimuthal quantum number m links the semiclassical results for the change in polar angle (θ → θ') to quantum results for an m → m' transition. Analytic formulas are derived that relate the location and width of peaks in the final polar angle distribution (PAD) to the K-dependence of the coefficients dK(j, j'), which are proportional to tensor cross sections σK(j → j'). Several special cases are treated that lead to final PADs that are approximately Lorentzian or sinc functions centered at θ' = θ. Another interesting case, "angular momentum reversal," was observed in the calculations for He. This phenomenon, which involves a reversal of the direction of the target's angular momentum, is shown to be associated with oscillatory behavior of the dK for certain transitions. Finally, several strategies for obtaining the dK coefficients from experimental data are discussed.
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Affiliation(s)
- T J Price
- Department of Physics, Lehigh University, 16 Memorial Drive East, Bethlehem, Pennsylvania 18015, USA
| | - A P Hickman
- Department of Physics, Lehigh University, 16 Memorial Drive East, Bethlehem, Pennsylvania 18015, USA
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Jones J, Richter K, Price TJ, Ross AJ, Crozet P, Faust C, Malenda RF, Carlus S, Hickman AP, Huennekens J. Rotationally inelastic collisions of excited NaK and NaCs molecules with noble gas and alkali atom perturbers. J Chem Phys 2017; 147:144303. [PMID: 29031279 DOI: 10.1063/1.4997577] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report measurements of rate coefficients at T ≈ 600 K for rotationally inelastic collisions of NaK molecules in the 2(A)1Σ+ electronic state with helium, argon, and potassium atom perturbers. Several initial rotational levels J between 14 and 44 were investigated. Collisions involving molecules in low-lying vibrational levels (v = 0, 1, and 2) of the 2(A)1Σ+ state were studied using Fourier-transform spectroscopy. Collisions involving molecules in a higher vibrational level, v = 16, were studied using pump/probe, optical-optical double resonance spectroscopy. In addition, polarization spectroscopy measurements were carried out to study the transfer of orientation in these collisions. Many, but not all, of the measurements were carried out in the "single-collision regime" where more than one collision is unlikely to occur within the lifetime of the excited molecule. The analysis of the experimental data, which is described in detail, includes an estimate of effects of multiple collisions on the reported rate coefficients. The most significant result of these experiments is the observation of a strong propensity for ΔJ = even transitions in collisions involving either helium or argon atoms; the propensity is much stronger for helium than for argon. For the initial rotational levels studied experimentally, almost all initial orientation is preserved in collisions of NaK 2(A)1Σ+ molecules with helium. Roughly between 1/3 and 2/3 of the orientation is preserved in collisions with argon, and almost all orientation is destroyed in collisions with potassium atoms. Complementary measurements on rotationally inelastic collisions of NaCs 2(A)1Σ+ with argon do not show a ΔJ = even propensity. The experimental results are compared with new theoretical calculations of collisions of NaK 2(A)1Σ+ with helium and argon. The calculations are in good agreement with the absolute magnitudes of the experimentally determined rate coefficients and accurately reproduce the very strong propensity for ΔJ = even transitions in helium collisions and the less strong propensity for ΔJ = even transitions in argon collisions. The calculations also show that collisions with helium are less likely to destroy orientation than collisions with argon, in agreement with the experimental results.
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Affiliation(s)
- J Jones
- Department of Physics, Lehigh University, 16 Memorial Drive East, Bethlehem, Pennsylvania 18015, USA
| | - K Richter
- Department of Physics, Lehigh University, 16 Memorial Drive East, Bethlehem, Pennsylvania 18015, USA
| | - T J Price
- Department of Physics, Lehigh University, 16 Memorial Drive East, Bethlehem, Pennsylvania 18015, USA
| | - A J Ross
- Institut Lumière Matiere, UMR 5306 Université Lyon I-CNRS, Université de Lyon, 69622 Villeurbanne, France
| | - P Crozet
- Institut Lumière Matiere, UMR 5306 Université Lyon I-CNRS, Université de Lyon, 69622 Villeurbanne, France
| | - C Faust
- Department of Physics, Lehigh University, 16 Memorial Drive East, Bethlehem, Pennsylvania 18015, USA
| | - R F Malenda
- Department of Physics, Lehigh University, 16 Memorial Drive East, Bethlehem, Pennsylvania 18015, USA
| | - S Carlus
- Department of Physics, Lehigh University, 16 Memorial Drive East, Bethlehem, Pennsylvania 18015, USA
| | - A P Hickman
- Department of Physics, Lehigh University, 16 Memorial Drive East, Bethlehem, Pennsylvania 18015, USA
| | - J Huennekens
- Department of Physics, Lehigh University, 16 Memorial Drive East, Bethlehem, Pennsylvania 18015, USA
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Price T, Towne A, Talbi D, Hickman A. Semiclassical model for the distribution of final polar angles and m′ states in rotationally inelastic collisions. Chem Phys Lett 2016. [DOI: 10.1016/j.cplett.2015.12.037] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Malenda RF, Price TJ, Stevens J, Uppalapati SL, Fragale A, Weiser PM, Kuczala A, Talbi D, Hickman AP. Theoretical calculations of rotationally inelastic collisions of He with NaK(A (1)Σ(+)): Transfer of population, orientation, and alignment. J Chem Phys 2015; 142:224301. [PMID: 26071704 DOI: 10.1063/1.4922161] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We have performed extensive calculations to investigate thermal energy, rotationally inelastic collisions of NaK (A(1)Σ(+)) with He. We determined a potential energy surface using a multi-reference configuration interaction wave function as implemented by the GAMESS electronic structure code, and we have performed coupled channel scattering calculations using the Arthurs and Dalgarno formalism. We also calculate the Grawert coefficients B(λ)(j, j') for each j → j' transition. These coefficients are used to determine the probability that orientation and alignment are preserved in collisions taking place in a cell environment. The calculations include all rotational levels with j or j' between 0 and 50, and total (translational and rotational) energies in the range 0.0002-0.0025 a.u. (∼44-550 cm(-1)). The calculated cross sections for transitions with even values of Δj tend to be larger than those for transitions with odd Δj, in agreement with the recent experiments of Wolfe et al. (J. Chem. Phys. 134, 174301 (2011)). The calculations of the energy dependence of the cross sections and the calculations of the fraction of orientation and alignment preserved in collisions also exhibit distinctly different behaviors for odd and even values of Δj. The calculations also indicate that the average fraction of orientation or alignment preserved in a transition becomes larger as j increases. We interpret this behavior using the semiclassical model of Derouard, which also leads to a simple way of visualizing the distribution of the angles between the initial and final angular momentum vectors j and j'. Finally, we compare the exact quantum results for j → j' transitions with results based on the simpler, energy sudden approximation. That approximation is shown to be quite accurate.
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Affiliation(s)
- R F Malenda
- Department of Physics, Lehigh University, 16 Memorial Dr. East, Bethlehem, Pennsylvania 18015, USA
| | - T J Price
- Department of Physics, Lehigh University, 16 Memorial Dr. East, Bethlehem, Pennsylvania 18015, USA
| | - J Stevens
- Department of Physics, Lehigh University, 16 Memorial Dr. East, Bethlehem, Pennsylvania 18015, USA
| | - S L Uppalapati
- Department of Physics, Lehigh University, 16 Memorial Dr. East, Bethlehem, Pennsylvania 18015, USA
| | - A Fragale
- Department of Physics, Lehigh University, 16 Memorial Dr. East, Bethlehem, Pennsylvania 18015, USA
| | - P M Weiser
- Department of Physics, Lehigh University, 16 Memorial Dr. East, Bethlehem, Pennsylvania 18015, USA
| | - A Kuczala
- Department of Physics, Lehigh University, 16 Memorial Dr. East, Bethlehem, Pennsylvania 18015, USA
| | - D Talbi
- Laboratoire Univers et Particules de Montpellier, UMR 5299, Université Montpellier, Place Eugène Bataillon, 34095 Montpellier, France
| | - A P Hickman
- Department of Physics, Lehigh University, 16 Memorial Dr. East, Bethlehem, Pennsylvania 18015, USA
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Han X, Yang J, Guan Y, Zhou Z, Zhao W, Allouche A, Magnier S, Ahmed E, Lyyra A, Dai X. Observation of the State of. Chem Phys Lett 2014. [DOI: 10.1016/j.cplett.2014.04.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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McGurk SJ, McKendrick KG, Costen ML, Alexander MH, Dagdigian PJ. Parity-dependent oscillations in collisional polarization transfer: CN(A²Π, v = 4) + Ar. J Chem Phys 2013; 139:124304. [PMID: 24089764 DOI: 10.1063/1.4821602] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report the first systematic experimental and theoretical study of the state-to-state transfer of rotational angular momentum orientation in a (2)Π-rare gas system. CN(X(2)Σ(+)) was produced by pulsed 266 nm photolysis of ICN in a thermal bath (296 K) of Ar collider gas. A pulsed circularly polarized tunable dye laser prepared CN(A(2)Π, v = 4) in two fully state-selected initial levels, j = 6.5 F1e and j = 10.5 F2f, with a known laboratory-frame orientation. Both the prepared levels and a range of product levels, j' F1e and j' F2f, were monitored using the circular polarized output of a tunable diode laser via cw frequency-modulated (FM) spectroscopy in stimulated emission on the CN(A-X) (4,2) band. The FM Doppler lineshapes for co-rotating and counter-rotating pump-and-probe geometries reveal the time-dependence of the populations and orientations. Kinetic fitting was used to extract the state-to-state population transfer rate constants and orientation multipole transfer efficiencies (MTEs), which quantify the degree of conservation of initially prepared orientation in the product level. Complementary full quantum scattering (QS) calculations were carried out on recently computed ab initio potential energy surfaces. Collision-energy-dependent tensor cross sections for ranks K = 0 and 1 were computed for transitions from both initial levels to all final levels. These quantities were integrated over the thermal collision energy distribution to yield predictions of the experimentally observed state-to-state population transfer rate constants and MTEs. Excellent agreement between experiment and theory is observed for both measured quantities. Dramatic oscillations in the MTEs are observed, up to and including changes in the sign of the orientation, as a function of even/odd Δj within a particular spin-orbit and e/f manifold. These oscillations, along with those also observed in the state-to-state rate constants, reflect the rotational parity of the final level. In general, parity-conserving collisions conserve rotational orientation, while parity-changing collisions result in large changes in the orientation. The QS calculations show that the dynamics of the collisions leading to these different outcomes are fundamentally different. We propose that the origin of this behavior lies in interferences between collisions that sample the even and odd-λ terms in the angular expansions of the PESs.
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Affiliation(s)
- S J McGurk
- School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom
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Ross AJ, Crozet P, Richard C, Harker H, Ashworth SH, Tokaryk DW. Resolved fluorescence spectra of NiH. Electronic structure, electronic energy transfer, and the Zeeman effect in low-lying states. Mol Phys 2012. [DOI: 10.1080/00268976.2012.655336] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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Ashman S, McGeehan B, Wolfe CM, Faust C, Richter K, Jones J, Hickman AP, Huennekens J. Experimental studies of the NaCs 5(3)Π0 and 1(a)3Σ+ states. J Chem Phys 2012; 136:114313. [PMID: 22443770 DOI: 10.1063/1.3689388] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report high resolution measurements of 372 NaCs 5(3)Π(0)(v, J) ro-vibrational level energies in the range 0 ≤ v ≤ 22. The data have been used to construct NaCs 5(3)Π(0) potential energy curves using the Rydberg-Klein-Rees and inverted perturbation approximation methods. Bound-free 5(3)Π(0)(v, J) → 1(a)(3)Σ(+) emission has also been measured, and is used to determine the repulsive wall of the 1(a)(3)Σ(+) state and the 5(3)Π(0) → 1(a)(3)Σ(+) relative transition dipole moment function. Hyperfine structure in the 5(3)Π(0) state has not been observed in this experiment. This null result is explained using a simple vector coupling model.
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Affiliation(s)
- S Ashman
- Department of Physics, 16 Memorial Dr. East, Lehigh University, Bethlehem, Pennsylvania 18015, USA
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Paterson G, Costen ML, McKendrick KG. Collisional depolarisation of rotational angular momentum: influence of the potential energy surface on the collision dynamics? INT REV PHYS CHEM 2012. [DOI: 10.1080/0144235x.2012.659046] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Paterson G, Costen ML, McKendrick KG. Collisional depolarization of rotational angular momentum: what are the observables and how can they be measured? Mol Phys 2011. [DOI: 10.1080/00268976.2011.621901] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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