Dynamics of conversion of atomic helium(triplet-2S) atoms to molecular helium(odd triplet-a-sigma-plus) molecules in ternary collisions (helium)

[摘要] The temperature dependence of conversion of He(2$sp3$S$sb1$) metastable atoms to He$sb2$(a$sp3Sigmasp+sb{m u}$) metastable molecules in the three-body reaction$$m He(2sp3Ssb1)+2He(1sp1Ssb0) o Hesb2(asp3Sigmasp+sb{u})+He(1sp1Ssb0)$$has been investigated over the temperature range 65K-700K. This reaction is thermally activated as a consequence of a long range repulsive barrier in the He(2$sp3$S$sb1)$-He(1$sp1$S$sb0$) interaction potential. The data reveal that there are two reaction channels with distinctly different activation energies. The temperature dependence of the measured rate coefficient $delta$(T) is accurately described by$$m delta(T) = lbrack 87.4 T exp({-}750/T){+}4.1T exp({-}200/T)brack imes 10sp{-37} cmsp{-6}secsp{-1}.$$The first activation energy, 750 $pm$ 70K(63 $pm$ 6meV), is equal to the known He(2$sp3$S$sb1)$-He(1$sp1$S$sb0$) repulsive barrier height. The second activation energy is 17 $pm$ 2 meV.

[发布机构] Rice University