6533b85bfe1ef96bd12bbdf2

RESEARCH PRODUCT

Ortho−ParaH2Conversion by Proton Exchange at Low Temperature: An Accurate Quantum Mechanical Study

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We report extensive, accurate fully quantum, time-independent calculations of cross sections at low collision energies, and rate coefficients at low temperatures for the ${\mathrm{H}}^{+}+{\mathrm{H}}_{2}(v=0,j)\ensuremath{\rightarrow}{\mathrm{H}}^{+}+{\mathrm{H}}_{2}(v=0,{j}^{\ensuremath{'}})$ reaction. Different transitions are considered, especially the ortho-para conversion ($j=1\ensuremath{\rightarrow}{j}^{\ensuremath{'}}=0$) 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 $4.15\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}\text{ }\text{ }{\mathrm{cm}}^{3}\text{ }{\mathrm{molecule}}^{\ensuremath{-}1}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$ 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 ($Tl100\text{ }\text{ }\mathrm{K}$).