Theoretical cross sections for H-on-Cs ionic and neutral reactions

Potential-energy curves and coupling matrix elements have been calculated for the CsH and CsH⁺ systems. The potentials and coupling terms were employed in the coupled equations where the nuclear motion is described classically to obtain the energy dependence of the cross sections for energies 0.1-3.0 keV. The cross sections so obtained were: Q₊₀ for the reaction H⁺ + Cs {→} H + Cs⁺, Q₊ₘ for H⁺+Cs→H(2s)+Cs⁺, Q_-0 for H^- + Cs⁺ {→} H + Cs, and Q_0- for H(1s)+Cs→H^-+Cs⁺. The CsH potential-energy curves were also used to estimate the ionization cross sections Q_ion-Cs for H^-+Cs→H^-+Cs⁺+e and Q_ion-H for H^-+Cs→H+Cs+e, and to yield an upper-limit cross section Q_m- for the reaction H(2s)+Cs→H^-+Cs⁺. Semiempirical calculations were employed to obtain the deactivation cross section Qmg for H(2s)+Cs→H(2p)+Cs where the product H(2p) rapidly radiates to H(1s). At 0.5 keV the theoretical cross sections obtained were Q₊₀=1.2×10^-14, Q₊ₘ=5.5×10^-15, Q_-0=1.5×10^-14, Q_0-=8.2×10^-16, Q_ion-Cs=1.3×10^-15, Q_ion-H=2.9×10^-15, Qmg=8.1×10^-15, and Q_m-≤4×10^-16 cm². For the reactions where experimental data is available, the theoretical cross sections are in satisfactory agreement with experiment except for Q_0-, where the theoretical values are approximately a factor of 5 larger than the experimental values.