Phys. Rev. A 80, 042507 (2009) [10 pages]Nuclear spin conversion in NH3Received 9 June 2009; published 14 October 2009 The nuclear spin conversion (NSC) rate for a gas sample of NH3 is calculated in the framework of the quantum relaxation model. It is based on the knowledge of the vibration-inversion levels of the lowest vibrational states, the relaxation rates, and the intramolecular magnetic interactions. The magnitudes of the spin-spin and spin-rotation interaction terms have been obtained with the help of ab initio calculations. The value of the NSC at 296 K for a pressure of 1 Torr is 3.23×10−6 s−1 for 14NH3 and 9.15×10−6 s−1 for 15NH3. A linear dependence of the NSC rates on the pressure is valid up to 1 atm for 14NH3 and up to 30 Torr for 15NH3, where quasidegenerate ortho/para pairs are present in the excited ν2=1 state. © 2009 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevA.80.042507
DOI:
10.1103/PhysRevA.80.042507
PACS:
33.15.−e, 31.30.Gs, 34.90.+q
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