Zeeman relaxation of N2 + (2Σ+) in collisions with 3He and 4He

Autor: Thierry Stoecklin, G. Guillon, A I Voronin
Rok vydání: 2007
Předmět:
Zdroj: The European Physical Journal D. 46:83-87
ISSN: 1434-6079
1434-6060
DOI: 10.1140/epjd/e2007-00313-4
Popis: We compare the cross sections for the transitions changing the projection of the total angular momentum of N2 +(2Σ) in collisions with 3He and 4He at very low collision energy. The fundamental states of the two nuclear spin isomers of N2 + are considered as well as the two fine structure levels of the first excited para level N=2. It is shown that the two fundamental states of the two nuclear spin isomers behave differently. For the fundamental para level N=0 of N2 +, the projection changing cross section is always negligible compared to the elastic one for both He isotopes. For the fundamental ortho level N=1 of N2 +, the spin-rotation interaction couples the different spin levels directly so the spin relaxation becomes a first order process. The associated resonances increase the projection changing cross section which remains smaller but becomes comparable with the elastic one. This is in contrast with the excited rotational levels of N2 +, which for the rotational deactivation and elastic channels are found to be equal around the resonances for the collisions involving 3He. These two channels are always larger than the projection changing one. We also find that, for transitions involving the fundamental rotational state, the domain of validity of the threshold laws discussed by Krems and Dalgarno [Phys. Rev. A 67, 050704 (2003)] for a potential decreasing faster than 1/r2 is shortened, due to the long range charge induced dipole potential. This effect is illustrated for the collisions of 3He with the fundamental para state of N2 +.
Databáze: OpenAIRE
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