Ortho-Para H2 Conversion by Proton Exchange at Low Temperature: An Accurate Quantum Mechanical Study

We report extensive, accurate fully quantum, time-independent calculations of cross sections at low collision energies, and rate coefficients at low temperatures for the H+ + H-2(v = 0, j) -> H+ + H-2(v = 0, j') reaction. Different transitions are considered, especially the ortho-para conversion (j = 1 -> j' = 0) which is of key importance in astrophysics. This conversion process appears to be very efficient and dominant at low temperature, with a rate coefficient of 4.15 x 10(-10) cm(3) molecule(-1) s(-1) at 10 K. The quantum mechanical results are also compared with statistical quantum predictions and the reaction is found to be statistical in the low temperature regime (T < 100 K).