15 research outputs found
Scattering of Stark-decelerated OH radicals with rare-gas atoms
We present a combined experimental and theoretical study on the rotationally
inelastic scattering of OH (X\,^2\Pi_{3/2}, J=3/2, f) radicals with the
collision partners He, Ne, Ar, Kr, Xe, and D as a function of the collision
energy between cm and 400~cm. The OH radicals are state
selected and velocity tuned prior to the collision using a Stark decelerator,
and field-free parity-resolved state-to-state inelastic relative scattering
cross sections are measured in a crossed molecular beam configuration. For all
OH-rare gas atom systems excellent agreement is obtained with the cross
sections predicted by close-coupling scattering calculations based on accurate
\emph{ab initio} potential energy surfaces. This series of experiments
complements recent studies on the scattering of OH radicals with Xe [Gilijamse
\emph{et al.}, Science {\bf 313}, 1617 (2006)], Ar [Scharfenberg \emph{et al.},
Phys. Chem. Chem. Phys. {\bf 12}, 10660 (2010)], He, and D [Kirste \emph{et
al.}, Phys. Rev. A {\bf 82}, 042717 (2010)]. A comparison of the relative
scattering cross sections for this set of collision partners reveals
interesting trends in the scattering behavior.Comment: 10 pages, 5 figure
The interaction of oh(x2π) with h2: Ab initio potential energy surfaces and bound states
Contains fulltext :
133240.pdf (publisher's version ) (Open Access
State-to-state inelastic scattering of stark-decelerated oh radicals with ar atoms
Contains fulltext :
99101.pdf (publisher's version ) (Open Access
Collisional excitation of NH by H2: Potential energy surface and scattering calculations
International audienceCollisional data for the excitation of NH by H2 are key to accurately derive the NH abundance in astrophysical media. We present a new four-dimensional potential energy surface (PES) for the NH-H2 van der Waals complex. The ab initio calculations of the PES were carried out using the explicitly correlated partially spin-restricted coupled cluster method with single, double, and perturbative triple excitations [RCCSD(T)-F12a] with the augmented correlation-consistent polarized valence triple zeta basis set. The PES was represented by an angular expansion in terms of coupled spherical harmonics. The global minimum corresponds to the linear structure with a well depth De = 149.10 cm−1. The calculated dissociation energy D0 is found to be 30.55 and 22.11 cm−1 for ortho-H2 and para-H2 complexes, respectively. These results are in agreement with the experimental values. Then, we perform quantum close-coupling calculations of the fine structure resolved excitation cross sections of NH induced by collisions with ortho-H2 and para-H2 for collisional energies up to 500 cm−1. We find strong differences between collisions induced by ortho-H2 and para-H2. Propensity rules are discussed. The cross sections are larger for fine structure conserving transitions than for fine structure changing ones, as predicted by theory. These new results should help in interpreting NH interstellar spectra and better constrain the abundance of NH in interstellar molecular clouds. © 2021 Author(s)
Rotationally inelastic scattering of OH by molecular hydrogen: Theory and experiment
Contains fulltext :
149632.pdf (publisher's version ) (Open Access
Hibridon: A program suite for time-independent non-reactive quantum scattering calculations
International audienceHibridon is a program package to solve the close-coupled equations which occur in the time independent quantum treatment of inelastic atomic and molecular collisions. Gas-phase scattering, photodissociation, collisions of atoms and/or molecules with flat surfaces, and bound states of weakly-bound complexes can be treated. From calculation of the S matrix, integral and differential cross sections, stereodynamic (alignment and steric asymmetry) cross sections, as well as more specialized quantities, such as transport and tensor cross sections, and cross sections between hyperfine levels, and photodissociation amplitudes can be obtained. The program is capable of treating closed-shell systems where the nuclear motion takes place on a single Born-Oppenheimer potential as well as open-shell systems for which the nuclear motion can evolve on several coupled electronic (Born-Oppenheimer) potentials. Program summary: Program Title: Hibridon CPC Library link to program files: https://doi.org/10.17632/sk9zcvz8vs.1 Developer's repository link: https://doi.org/10.5281/zenodo.7551616 Licensing provisions: GPLv3 Programming language: Fortran 90 External routines/libraries: LAPACK, BLAS Nature of problem: Solution of the time-independent Schrödinger equation for the inelastic scattering of atoms and molecules, for the photodissociation of molecules, and for the ro-vibrational motion of weakly bound molecular complexes. Solution method: The scattering wavefunction is expanded in a set of internal states of the system, constructed as direct products of the internal states of one (or both) fragments and angular functions which describe the rotation of one collision partner about the other. The Schrödinger equation for the nuclear motion is solved by determining the expansion coefficients as a function of the interparticle separation starting from the short-range classically forbidden region outwards to the asymptotic region. The S matrix is given by the asymptotic behavior of the wavefunction. Integral and differential cross sections, as well as other scattering and photodissociation quantities are calculated from the S matrix
Resonances in rotationally inelastic scattering of NH3 and ND3 with H2
We present theoretical studies on the scattering resonances in rotationally inelastic collisions of NH3 and ND3 molecules with H2 molecules. We use the quantum close-coupling method to compute state-to-state integral and differential cross sections for the NH3/ND3-H2 system for collision energies between 5 and 70 cm-1, using a previously reported potential energy surface [Maret et al. Mon. Not. R. Astron. Soc. 399, 425 (2009)]. We identify the resonances as shape or Feshbach resonances. To analyze these, we use an adiabatic bender model, as well as examination at the scattering wave functions and lifetimes. The strength and width of the resonance peaks suggest that they could be observed in a crossed molecular beam experiment involving a Stark-decelerated NH3 beam.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Rotationally inelastic scattering of ND3 with H-2 as a probe of the intermolecular potential energy surface
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