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Detection of Microwave Transitions between Ortho and Para States in a Free Isolated Molecule

Hideto Kanamori, Zeinab. T. Dehghani, Asao Mizoguchi, and Yasuki Endo
Phys. Rev. Lett. 119, 173401 – Published 25 October 2017
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Abstract

Microwave transitions between the ortho and para states of the S2Cl2 molecule in a free isolated condition are observed for the first time. In the theoretical treatment, we derive eigenfunctions of an effective Hamiltonian including the ortho-para interaction to calculate the intensities and frequencies of forbidden ortho-para transitions in the cm-wave region and pick up some promising candidates for the spectroscopic detection. In the experiment, transitions of the S2Cl2 molecule under a supersonic jet condition are observed with a Fourier transform microwave spectrometer. Seven hyperfine resolved rotational transitions including the lowest rotational level are detected as the ortho-para transitions at the predicted frequencies within the experimental errors. The observed intensities are about 103 times the allowed transitions, which are consistent with the predictions based on the intensity-borrowing model. This result suggests that the ortho-para conversion of this molecule occurs in a few thousand years through spontaneous emission even in a circumstance where molecular collisions occur rarely like in interstellar space.

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  • Received 9 August 2017

DOI:https://doi.org/10.1103/PhysRevLett.119.173401

© 2017 American Physical Society

Physics Subject Headings (PhySH)

Atomic, Molecular & Optical

Synopsis

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Detection of Ortho-Para Transition in Molecules

Published 25 October 2017

Microwave emission from a simple molecule reveals a highly forbidden transition between two nuclear spin states.

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Authors & Affiliations

Hideto Kanamori1,*, Zeinab. T. Dehghani1, Asao Mizoguchi1, and Yasuki Endo2

  • 1Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551, Japan
  • 2Department of Applied Chemistry, National Chiao, Tung University, Hsinchu 30010, Taiwan

  • *Corresponding author. kanamori@phys.titech.ac.jp

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Issue

Vol. 119, Iss. 17 — 27 October 2017

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