Spin exchange and redistribution of the spin-polarization at the interaction between ground state alkali atoms and nitrogen atoms in gas discharge

Full text: In gas discharge an effective spin-exchange process is proceeding between spin-polarized ground state alkali atoms and ground state's nitrogen atoms, that demonstrates a conservation of total electron spin and, consequently, a transfer of angular momentum from an ensemble of the previously spin-polarized alkali atoms to the electronic part of the N atoms in 4S3/2 state. Consider the behavior of a quasi-molecular system consists of the nitrogen atom with electron spin angular momentum SA = 3/2, and alkali atom with electron spin angular momentum SB = 1/2. If the spins of the two interacting particles be SA and SB, there are two molecular states Vi, which correspond to different values of the total spin (S) of the quasi-molecule. In our case there are two molecular terms Vq(S = 2) and Vt(S = 1). Therefore the spin-exchange process can be described by two cross sections σ1 and σ2 corresponding to the change in the magnetic quantum numbers of the interacting particles, respectively, 3/2,1/2 ↔ 3/2,-1/2; -3/2,1/2 ↔ -1/2,-1/2;3/2,-1/2 ↔ 1/2,1/2; -1/2,-1/2 ↔ -3/2,1/2 and -1/2,-1/2 ↔ 1/2,-1/2; 1/2,-1/2 ↔ -1/2,1/2. It can be shown that the cross sections are determined as σ1 = 3/4|fq - ft|2 and σ2 = 1/4|fq - ft|2, where fq and ft are the scattering amplitudes on the quintet Vtq and triplet Vt terms. At the recombination of the spin-polarized N atoms the polarization can be transmitted to the N2 molecules. The mechanism of the N atoms recombination involves nitrogen atom recombination into the N2(A5Σ) state. At the conservation of angular momentum during the interaction the transfer of angular momentum from atoms to molecules takes place being to the spin-polarization of the N2 molecule. The redistribution of angular momentum between electron spin system and rotational system in the N2 molecule results in rotational polarization of the molecule too. In this work the kinetics of optical orientation and spin-exchange collisions between alkali and nitrogen atoms have been investigated and equations, describing the evolutions of the polarized moments have been received. The equations describing the redistribution of the polarization in the N2 have been received too. (author)