State-to-state resolved differential cross sections for rotationally inelastic scattering of ND3 with He

Ondrej Tkac, Ashim Kumar Saha, Jolijn Onvlee, Chung-Hsin Yang, Gautam Sarma, Chandan Kumar Bishwakarma, Sebastiaan Y. T. van de Meerakker, Ad van der Avoird*, David H. Parker, Andrew J. Orr-Ewing

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)

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Abstract

State-to-state differential cross sections are reported for rotationally inelastic scattering of fully state-selected ND3 (j(k)(perpendicular to) = 1(1)(-)) with He. Experimental measurements are compared with full close-coupling quantum-mechanical scattering calculations that used an ab initio potential energy surface. Results are presented for final states up to j(k')'(+/-) = 7(7)(-) at a mean collision energy of 430 cm(-1). For selected final quantum states, the effect of collision energy on the differential cross sections is also explored in the range 230-720 cm(-1). For the experimental studies, a hexapole electrostatic lens was used for the j(k)(+/-) state-selection of ND3 molecules in their electronic and vibrational ground states in a molecular beam. This state-selected molecular beam was then crossed with a beam of He atoms. The velocities of inelastically scattered ND3 molecules in single j(k')'(+/-) states were obtained by velocity map imaging, and converted to differential cross sections in the centre-of-mass frame by density-to-flux transformation. The close-coupling calculations reproduce well the measured angular distributions. For small changes in the rotational angular momentum quantum number (j), the ND3 is predominantly forward scattered, but the scattering shifts to the sideways and backward directions as Delta j increases. For scattering into a given j(k')'(perpendicular to) state, cross-sections for collisions that conserve the +/- symmetry associated with the ND3 inversion vibration are larger and generally more forward scattered than the corresponding symmetry-changing processes.

Original languageEnglish
Pages (from-to)477-488
Number of pages12
JournalPhysical Chemistry Chemical Physics
Volume16
Issue number2
Early online date25 Sep 2013
DOIs
Publication statusPublished - 25 Sep 2013

Keywords

  • POTENTIAL-ENERGY SURFACE
  • MICROWAVE EMISSION
  • BEAM SCATTERING
  • AB-INITIO
  • AMMONIA
  • NH3
  • EXCITATION
  • COLLISIONS
  • PHOTOELECTRON
  • SPECTROSCOPY

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