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 vibra- tional 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 3.23x10−6 s−1 for 14NH3 and 9.15x10−6 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 v2=1 state.
P. Cacciani, J. Cosléou, M. Khelkhal, M. Tutorie, C. Puzzarini, P. Pracna (2009). Nuclear spin conversion in NH3. PHYSICAL REVIEW A, 80, 042507/1-042507/10 [10.1103/PhysRevA.80.042507].
Nuclear spin conversion in NH3
PUZZARINI, CRISTINA;
2009
Abstract
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 vibra- tional 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 3.23x10−6 s−1 for 14NH3 and 9.15x10−6 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 v2=1 state.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
