Temperature dependence of spin exchange frequency shifts in H-H collisions

Abstract

Experimental data on the spin exchange frequency shifts due to hydrogen-hydrogen spin exchange collisions are reported over the temperature range 77 K to 363 K. They are found to agree with the results of a theoretical calculation of the temperature dependence of the spin exchange frequency shift cross-section and with an experimental result obtained by a different technique near room temperature. Our experimental results confirm the prediction that the spin exchange frequency shift cross-section changes sign at low temperature