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Parity-dependent rotational rainbows in and He–NO differential collision cross sections
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10.1063/1.2234771
/content/aip/journal/jcp/125/13/10.1063/1.2234771
http://aip.metastore.ingenta.com/content/aip/journal/jcp/125/13/10.1063/1.2234771
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

(Color) Set of raw experimental ion images for spin-orbit conserving scattering. The images for are collected using the spectroscopic branch. The majority of the images for are collected via the branch; those labeled with a star are from the combined branch that exhibits more asymmetry with respect to the . This is due to the combination of collision-induced alignment and the residence time of the molecules in the detection region. For a and branch transition the effects of alignment and residence time nearly cancel, while for branch transitions these add, yielding very asymmetric ion images. The images are plotted such that two images above each other relate to the same parity pair . The missing image for , could not be collected due to overlapping spectral lines.

Image of FIG. 2.
FIG. 2.

The rotational levels of the NO molecule are labeled with their rotational quantum number and symmetry index . Recall that parity and relate as . The parity pair numbers in this figure relate to the experimental case where the incoming state is given by , . Parity pairs are observed for both spin-orbit conserving as for spin-orbit changing transitions, but the differential cross sections of a parity pair for spin-orbit conserving transitions does not correspond to that of the same pair for a spin-orbit changing collision. The energy differences are taken arbitrarily and are not scaled to the actual values.

Image of FIG. 3.
FIG. 3.

Differential cross sections for scattering into . The differential cross sections are plotted per parity pair and normalized such that the integral . The differential cross section for , is plotted separately in Fig. 5.

Image of FIG. 4.
FIG. 4.

Differential cross sections for scattering into . The differential cross sections are plotted per parity pair and normalized such that the integral . The differential cross section for , is plotted separately in Fig. 5.

Image of FIG. 5.
FIG. 5.

Differential cross sections for scattering into the highest observed rotational state of the lower component of the doublet . Note that the differential cross section for , has a strong sideways scattered contribution. From a simple classical model this cannot be understood. A similar, but even more pronounced effect has been observed for He–NO collisions (Ref. 18).

Image of FIG. 6.
FIG. 6.

Differential cross sections for (He–NO) scattering into . The differential cross sections are plotted per parity pair and normalized such that the integral .

Image of FIG. 7.
FIG. 7.

Differential cross sections for (He–NO) scattering into . The differential cross sections are plotted per parity pair and normalized such that the integral .

Image of FIG. 8.
FIG. 8.

The positions of the rotational rainbows for each parity pair are plotted for both and He–NO scattering. The upper panel shows the rainbow maxima for spin-orbit conserving collisions, while the lower panel shows the rainbow maxima for spin-orbit changing collisions. The results are averaged over both components of the pairs. To guide the eyes, the points for He–NO and are connected via lines. The dotted line in the upper panel follows from a fit of parameters and of Eq. (9) to the data points.

Image of FIG. 9.
FIG. 9.

Schematic representation of a hard ellipsoid NO shell colliding with a molecule. The incoming linear momentum is decomposed into a component parallel and one perpendicular to the hard shell. The parallel component is conserved during collision, while the perpendicular one is partly transferred into rotation.

Image of FIG. 10.
FIG. 10.

Experimental He–NO rainbow maxima from Fig. 8 are compared to values from CC calculations (Ref. 18). Results for spin-orbit conserving transitions are found in the upper panel, while the lower panel shows results for spin-orbit changing transitions. The maxima for parity changing transitions are at larger scattering angles than those for parity conserving transitions . To elucidate this, separate lines are drawn that connect the data points for both cases. The filtering of the data causes a slight underestimation of the scattering angle with maximum differential cross section when it is close to 180°.

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/content/aip/journal/jcp/125/13/10.1063/1.2234771
2006-10-04
2014-04-16
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Parity-dependent rotational rainbows in D2–NO and He–NO differential collision cross sections
http://aip.metastore.ingenta.com/content/aip/journal/jcp/125/13/10.1063/1.2234771
10.1063/1.2234771
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