Nuclear spin symmetry conservation studied by cavity ring-down spectroscopy of ammonia in a seeded supersonic jet from a pulsed slit nozzle. (2nd June 2020)

• Record Type: Journal Article
• Authors: Wichmann, G.; Miloglyadov, E.; Seyfang, G.; Quack, M.
• Is Part Of: Molecular physics. Volume 118:Number 11(2020)
• Publication Date: 2020-06-02
• Subjects: Nuclear spin symmetry -- supersonic jet expansion -- cavity ring-down absorption spectroscopy -- NH3 -- mid-IR high-resolution laser spectroscopy; Molecules -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Molécules -- Périodiques; Chimie physique et théorique -- Périodiques; 539.6.05
• DOI: 10.1080/00268976.2020.1752946
• Languages: English
• ISSNs: 0026-8976

Abstract

Abstract : We report high-resolution cw laser spectra of the symmetric stretching fundamental in ammonia 14 NH 3 measured with a cavity ring-down setup for mid-IR transitions (around 3300 c m − 1 ). In a supersonic jet expansion ( 0.0001 ≤ x ( N H 3 ) ≤ 0.04 seeded in Ar), we have obtained rotational temperatures below 7 K . For the gas expansion, a pulsed slit nozzle with 40 m m length and 70 µm width has been used. The measured relative line intensities demonstrate that the A and E nuclear spin symmetry isomers do not interconvert in the supersonic jet expansion under these conditions (nuclear spin symmetry conservation). The lateral velocity of the gas expansion has been probed by a Doppler profile measurement, showing a preference for an expansion with an angular distribution following Lambert's cosine law perpendicular to the slit direction and an approximate molecular velocity of about 470 m / s . The experimental setup is described in detail, also in view of high-resolution spectroscopy of chiral molecules as candidates to measure the parity violating energy difference between enantiomers with a barrier to interconversion around 2500 c m − 1 . GRAPHICAL ABSTRACT: