State-to-state differential cross sections for spin–multiplet-changing collisions of NO(X 2Π1/2) with argon

Abstract

Rotational state-resolved differential cross sections (DCS) for spin–multiplet-changing collisions of NO(X 2Π1/2→X 2Π3/2) with Ar are presented and compared to results from previous experimental and theoretical studies performed on the NO/Ar system. A crossed molecular beam apparatus coupled with velocity-mapped ion imaging was used to measure complete (θ=0°–180°) DCS for scattering of NO(X 2Π1/2,j=0.5) into NO(X 2Π3/2,j′) rotational states ranging from j′=1.5 to j′=12.5. Scattered products were detected by state-selective ionization using (1+1′) resonance-enhanced multiphoton ionization via the A 2Σ+ state. State-to-state DCS were extracted in the center-of-mass frame of reference for energy transfer at a center-of-mass collision energy of ∼530 cm−1. Studies performed using horizontally and vertically polarized excitation laser beams yielded DCS which were remarkably similar, indicating that state-to-state scattering for this system is insensitive to probe beam polarization. Experimentally determined angular scattering distributions show primarily forward scattering for low-energy rotational states (j<7.5), with side- and back-scattering increasing with product angular momentum. The scattering results are compared and contrasted to results from earlier experimental investigations and to theoretical results from quantum close-coupling calculations based on ab initio coupled cluster CCSD(T) potential energy surfaces.

Attractive and repulsive interactions in the inelastic scattering of NO by Ar: A comparison between classical trajectory and close-coupling quantum mechanical results

“…These were found to be in excellent agreement with the most recent crossed-beam ion imaging experiments for both transitions in which the initial spin-orbit state ͑⍀ϭ1/2͒ is conserved as well as for transitions in which rotational excitation is accompanied by spinorbit excitation ͑⍀ϭ1/2→3/2͒. 22,23 Since rotational excitation from the ground ( jϭ0.5) rotational level of NO up to jЈϭ15.5 was investigated, the repulsive wall of the potential is clearly probed in these studies. However, since the nominal collision energy in the experiments ͑66 meV͒ is only roughly five times larger than the depth of the potential well, 28 and since the NO molecule has a small rotational constant (Bϭ1.7 cm Ϫ1 ), attractive interactions could also play an important role in excitation of the lower rotational states.…”

“…a͒ Author to whom correspondence should be addressed. Fax: ϩ34 91394 4135; Electronic mail: aoiz@legendre.quim.ucm.es Over the past two decades collisions of Ar with NO(X 2 ⌸) have been the subject of intense experimental [13][14][15][16][17][18][19][20][21][22][23] and theoretical 15,24 -29 investigation. The open-shell character of the NO molecule has stimulated particular interest.…”

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

“…Also Kohguchi et al 21 reported discrepancies between theory and experiment for Ar-NO differential cross sections. Elioff et al 11 repeated these measurements for spin-orbit changing collisions and found a better correspondence to theory for the ratio between forward-and backward-scattered molecules than in Kohguchi's work. The experiment described in this work is the first scattering experiment in which differential cross sections for a͒ Present address: Sackler Laboratory for Astrophysics, Leiden Observatory, The Netherlands.…”

“…The velocity-mapped ion-imaging technique is now commonly used in the field of molecular dynamics. [7][8][9][10][11][12][13][14][15] Differential cross sections for inelastic collisions can also be measured using a movable detector, 16 but this technique is more time consuming and experimentally difficult. The resolution depends on the scattering angle and only the scattering angle of the molecule in the laboratory frame can be obtained.…”

Rotationally Inelastic Scattering of Quantum-State-Selected ND3with Ar

“…[16][17][18][19][20] Recently, the inelastic scattering dynamics of methyl radical with He, 21 H2 and D2, 22 and Ar 23 were examined using crossed molecular beam methods in combination with velocity map imaging (VMI …”