We derive an expression for the diffusion cross section of identical atoms and use it in a report of diffusion, viscosity, total, spin-change, frequency-shift, and broadening cross sections in hydrogen, calculated with improved interaction potentials. We also report some total cross sections for spin-polarized hydrogen.
Collisions of alkali-metal atoms in the ground state with the electron spin S = 1/2 are accompanied by exchange of electron coordinates between colliding particles, which leads to polarization transfer between them (i.e., to the well-known phenomenon of spin exchange). In addition, along with the polarization transfer from one partner to another, the magnetic resonance lines of colliding atoms are broadened and shifted in spin-exchange collisions. In particular the last two processes depend on the complex spin-exchange cross section. The real part of the cross section determines the so-called "spin-exchange cross section," which is responsible for the broadening of magnetic resonance lines, while the imaginary part determines the shift cross section, which governs the frequency shift of magnetic resonance. In order to describe the spin-exchange process one have to know complex spin-exchange cross sections. Complex spin-exchange cross sections are calculated on the basis of the data on the singlet (X 1 Σ + ) and triplet (a 3 Σ + ) potentials describing the interaction alkali-metal atoms in the ground state. Collisions of alkali-metal atoms Cs, Rb, K, Na in the ground state are considered in the energy interval of 10 −4 −10 −2 au.
Abstract The spin-exchange cross sections and the magnetic resonance frequency shift in collision of lithium and cesium atoms in the ground state are calculated. The calculations are performed based on the data on the singlet (X1Σ+) and triplet (a3Σ+) interaction potentials of 7Li 133Cs dimer. The passage from the energy dependences of the real and imaginary parts of the complex spin-exchange cross section to the temperature dependences makes it possible to obtain information on both the broadening and the frequency shift of the magnetic resonance line in collisions of the atoms under study.