Steric asymmetry in state-resolved NO–Ar collisions

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122

The first measurements of differential inelastic collision cross sections of fully state-selected NO ͑j =1/2, ⍀ =1/2, ⑀ =−1͒ with He are presented. Full state selection is achieved by a 2 m long hexapole, which allows for a systematic study of the effect of parity conservation and breaking on the differential cross section. The collisionally excited NO molecules are detected using a resonant ͑1+1Ј͒ REMPI ionization scheme in combination with the velocity-mapped, ion-imaging technique. The current experimental configuration minimizes the contribution of noncolliding NO molecules in other rotational states j , ⍀ , ⑀ -that contaminates images-and allows for study of the collision process at an unprecedented level of detail. A simple method to correct ion images for collision-induced alignment is presented as well and its performance is demonstrated. The present results show a significant difference between differential cross sections for scattering into the upper and lower component of the ⌳-doublet of NO. This result cannot be due to the energy splitting between these components.

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Differential cross sections for collisions of hexapole state-selected NO with He

Gijsbertsen

Linnartz

Rus

et al. 2005

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122

“…Previous studies of inelastic scattering with Ar concentrated mostly on NO, [8][9][10][31][32][33][34][35][36][37][38][39] OH, 18,21,22,24 and HCl, 40 although scattering of a polyatomic molecule with Ar has been explored in the case of NH 3 . 41,42 Molecular nitrogen was previously used as a collider in studies of the inelastic scattering of HCl.…”

Section: Introductionmentioning

confidence: 99%

Rotationally inelastic scattering of methyl radicals with Ar and N2

Tkáč

Stei

Orr-Ewing

et al. 2015

Articles you may be interested inThe rotationally inelastic scattering of methyl radical with Ar and N 2 is examined at collision energies of 330 ± 25 cm −1 and 425 ± 50 cm −1 , respectively. Differential cross sections (DCSs) were measured for different final n ′ rotational levels (up to n ′ = 5) of the methyl radicals, averaged over k ′ sub-levels, using a crossed molecular beam machine with velocity map imaging. For Ar as a collision partner, we present a newly constructed ab initio potential energy surface and quantum mechanical scattering calculations of state-resolved DCSs. These computed DCSs agree well with the measurements. The DCSs for both Ar and N 2 collision partners are strongly forward peaked for all spectroscopic lines measured. For scattering angles below 60 • , the theoretical CD 3 -Ar DCSs show diffraction oscillations that become less pronounced as n ′ increases, but these oscillations are not resolved experimentally. Comparisons are drawn with our recently reported DCSs for scattering of methyl radicals with He atoms. C 2015 AIP Publishing LLC. [http://dx

“…It is a radical, with nonzero angular momentum in its rotational ground state, while it is stable enough to be stored in a gas bottle. Furthermore, it is easily detected with spectroscopic methods such as laser induced fluorescence 14 ͑LIF͒ and resonance enhanced multiphoton ionization 10,15 ͑REMPI͒. Using the hexapole focusing technique, 16 NO can be fully selected into a single quantum state ͑upper component of the ⌳ doublet͒ as it undergoes a first order Stark effect.…”

Section: Introductionmentioning

confidence: 99%

Parity-dependent rotational rainbows in D2–NO and He–NO differential collision cross sections

Gijsbertsen

Linnartz

Stolte

2006

The ͑jЈ , ⍀ Ј, ⑀Ј͒ dependent differential collision cross sections of D 2 with fully state selected ͑j =1/2, ⍀ =1/2, ⑀ =−1͒ NO have been determined at a collision energy of about 550 cm −1 . The collisionally excited NO molecules are detected by ͑1+1Ј͒ resonance enhanced multiphoton ionization combined using velocity-mapped ion-imaging. The results are compared to He-NO scattering results and tend to be more forward scattered for the same final rotational state. Both for collisions of the atomic He and the molecular D 2 with NO, scattering into pairs of rotational states with the same value of n = jЈ − ⑀⑀Ј/ 2 yields the same angular dependence of the cross section. This "parity propensity rule" remains present both for spin-orbit conserving and spin-orbit changing transitions. The maxima in the differential cross sections-that reflect rotational rainbows-have been extracted from the D 2 -NO and the He-NO differential cross sections. These maxima are found to be distinct for odd and even parity pair number n. Rainbow positions of parity changing transitions ͑n is odd͒ occur at larger scattering angles than those of parity conserving transitions ͑n is even͒. Parity conserving transitions exhibit-from a classical point of view-a larger effective eccentricity of the shell. No rainbow doubling due to collisions onto either the N-end or the O-end was observed. From a classical point of view the presence of a double rainbow is expected. Rotational excitation of the D 2 molecules has not been observed.