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Theoretical investigation of rotationally inelastic collisions of CH2(ã) with helium
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10.1063/1.3575200
/content/aip/journal/jcp/134/15/10.1063/1.3575200
http://aip.metastore.ingenta.com/content/aip/journal/jcp/134/15/10.1063/1.3575200

Figures

Image of FIG. 1.
FIG. 1.

Body-frame coordinate system used to specify the orientation of the helium atom with respect to the center of mass of the CH() molecule. The body-frame axis is defined to lie along the inertial axis of the molecule. The molecule lies in the -plane. Note that the origin is at the center of mass, which is displaced toward negative by 0.19 bohr from the C atom

Image of FIG. 2.
FIG. 2.

Dependence of the potential energy (in cm−1) on the orientation of the helium with respect to the CH() molecule for an atom–molecule separation = 4.58 bohr.

Image of FIG. 3.
FIG. 3.

Contour plot of the highest-occupied molecular orbital (3 ) of the CH() molecule. This is the higher in energy of the two bonding molecular orbitals (1 and 3 ).

Image of FIG. 4.
FIG. 4.

Dependence on the He–CH() distance of the larger of the expansion coefficients v [defined in Eq. (1) ].

Image of FIG. 5.
FIG. 5.

Dependence of the potential energy for the interaction of CH() with helium upon the angle for = 90° at several values of the atom–molecule separation (given in bohr). The motion shown here corresponds to rotation of the He atom in the -plane in Fig. 1 .

Image of FIG. 6.
FIG. 6.

Rotational levels of (solid) and (dashed) of CH() with energies less than 500 cm−1. The levels are grouped by column according to the value of the prolate-limit body-frame projection quantum number . The individual rotational levels are labeled by the total angular momentum and by its projections along the and inertial axes: and .

Image of FIG. 7.
FIG. 7.

Bar plot of the cross sections for rotationally inelastic scattering of CH() in the = 4 and 5, = 1 levels by collision with He at a collision energy of 300 cm−1. The initial level is denoted by a dark box.

Image of FIG. 8.
FIG. 8.

Bar plot of the cross sections for rotationally inelastic scattering of CH() in the = 4 and 5, = 1 levels by collision with He at a collision energy of 300 cm−1. The initial level is denoted by a dark box.

Image of FIG. 9.
FIG. 9.

Bar plot of the cross sections for rotationally inelastic scattering of CH() in the = 4, = 1 level by collision with He at a collision energy of 300 cm−1, plotted here against the energy gap, with Δ = ( , ) – ( k). The square at 0 cm−1 denotes the initial level.

Image of FIG. 10.
FIG. 10.

(a) Rotationally inelastic total removal cross section for the lower = 1 and rotational levels of CH() in collisions with He at a collision energy of 300 cm−1. (b) Similar plot but for the rotationally inelastic total removal rates constants at 298 K.

Image of FIG. 11.
FIG. 11.

Dependence upon the collision energy of the state-to-state integral cross sections for rotational transitions out of the lowest levels of the (a) [0] and (b) [1] nuclear spin modifications of CH() in collisions with helium. Only the dominant transitions are plotted.

Image of FIG. 12.
FIG. 12.

Dependence upon the collision energy of the rotationally inelastic total removal cross sections for the = 1 (a) and (b) levels of CH() in collisions with helium. The value of the angular momentum is indicated beside each curve.

Image of FIG. 13.
FIG. 13.

Dependence upon the collision energy of the = 2 elastic depolarization cross sections for the = 1 (a) and (b) levels of CH() in collisions with helium. The value of the angular momentum is indicated beside each curve.

Image of FIG. 14.
FIG. 14.

Computed rate constants for elastic depolarization of the rank = 1 and 2 multipoles (orientation and alignment, respectively) of the (a) and (b) = 1 levels of CH() in collisions with helium.

Image of FIG. 15.
FIG. 15.

Elastic depolarization cross sections of the = 1–3 rotational levels of and CH() in collisions with helium at a collision energy of 300 cm−1. For each value of , the levels (labeled also by and , see Fig. 6 ) are ordered in increasing energy from left to right.

Image of FIG. 16.
FIG. 16.

Rate constants for collisional removal by rotational transitions and for elastic depolarization of alignment ( = 2) for CH() = 1 levels in collisions with helium. The theoretical values were computed in the present study, while the experimental values were taken from the investigation by Hall, Sears, and their co-workers [Ref. 21 ]. The = 8 level of this manifold is known to be strongly perturbed by a vibration-rotation level of the 3 state (Ref. 20 ). The labels and denote the experimentally observed rate constants for the two perturbed levels of predominantly singlet and triplet character, respectively.

Tables

Generic image for table
Table I.

Overall inelasticity of = 4, = 1 and = 5, = 1 rotational levels of and CH() in collisions with helium at a collision energy of 300 cm−1.

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/content/aip/journal/jcp/134/15/10.1063/1.3575200
2011-04-21
2014-04-21
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Theoretical investigation of rotationally inelastic collisions of CH2(ã) with helium
http://aip.metastore.ingenta.com/content/aip/journal/jcp/134/15/10.1063/1.3575200
10.1063/1.3575200
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