Qianli Ma

Publications (3)6.19 Total impact

• Article: Theoretical study of the vibrational relaxation of the methyl radical in collisions with helium.

  Qianli Ma, Paul J Dagdigian, Millard H Alexander
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  ABSTRACT: We report a theoretical investigation of the relaxation of the umbrella vibrational mode (the ν2 mode) of the CH3 molecule in its ground X̃(2)A2 ('') electronic state in collisions with helium. We have calculated a four-dimensional potential energy surface (PES) for the interaction between CH3 with different umbrella displacements and a helium atom, using a restricted open-shell coupled-cluster method with inclusion of all single, double, and (perturbatively) triple excitations [RCCSD(T)]. With this PES we carried out full close-coupling scattering calculations including all CH3 umbrella-rotational levels with v2 ≤ 3. To our knowledge, this work represents the first fully quantum calculations of ro-vibrational relaxation of a polyatomic. In more detail, we investigate propensities in the calculated ro-vibrational cross sections and the dependence on initial rotational excitation, as well as determining thermal rate constants. Overall, ro-vibrational relaxation is nearly two orders of magnitude less efficient than pure-rotational relaxation, with a noticeable dependence on the initial rotational level. We predict the room temperature v2 = 1 vibrational relaxation rate constant to be 5.4 × 10(-12) cm(3) molecule(-1) s(-1), compared to the rate constants for pure-rotational relaxation of the lower rotational levels (∼2.0 × 10(-10) cm(3) molecule(-1) s(-1)).
  The Journal of chemical physics 03/2013; 138(10):104317. · 3.09 Impact Factor
• Article: Resonances in rotationally inelastic scattering of OH(X2Π) with helium and neon.

  Koos B Gubbels, Qianli Ma, Millard H Alexander, Paul J Dagdigian, Dick Tanis, Gerrit C Groenenboom, Ad van der Avoird, Sebastiaan Y T van de Meerakker
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  ABSTRACT: We present detailed calculations on resonances in rotationally and spin-orbit inelastic scattering of OH (X(2)Π, j = 3/2, F(1), f) radicals with He and Ne atoms. We calculate new ab initio potential energy surfaces for OH-He, and the cross sections derived from these surfaces compare well with the recent crossed beam scattering experiment of Kirste et al. [Phys. Rev. A 82, 042717 (2010)]. We identify both shape and Feshbach resonances in the integral and differential state-to-state scattering cross sections, and we discuss the prospects for experimentally observing scattering resonances using Stark decelerated beams of OH radicals.
  The Journal of chemical physics 04/2012; 136(14):144308. · 3.09 Impact Factor
• Source

  Available from: Paul J Dagdigian

  Article: Resonances in rotationally inelastic scattering of OH($X^2\Pi$) with helium and neon

  Koos B. Gubbels, Qianli Ma, Millard H. Alexander, Paul Dagdigian, Dick Tanis, Gerrit C. Groenenboom, Ad van der Avoird, Sebastiaan Y. T. van de Meerakker
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  ABSTRACT: We present detailed calculations on resonances in rotationally and spin-orbit inelastic scattering of OH ($X\,^2\Pi, j=3/2, F_1, f$) radicals with He and Ne atoms. We calculate new \emph{ab initio} potential energy surfaces for OH-He, and the cross sections derived from these surfaces compare favorably with the recent crossed beam scattering experiment of Kirste \emph{et al.} [Phys. Rev. A \textbf{82}, 042717 (2010)]. We identify both shape and Feshbach resonances in the integral and differential state-to-state scattering cross sections, and we discuss the prospects for experimentally observing scattering resonances using Stark decelerated beams of OH radicals.
  01/2012;