Quantum dynamics of the O+OH reaction: from ultracold collisions to astrochemistry

We present quantum dynamics of the O+OH$ \to$ H+O$_2$ reaction at temperatures ranging from the ultracold limit to astrophysically relevant values. Two different potential energy surfaces for the HO$_2$ system are employed in the calculations and the sensitivity of the rate coefficients to the details of the interaction potential is explored. The zero-temperature limiting value of the rate coefficient is predicted to be about $6 \times 10^{-12}$ cm$^3$ s$^{-1}$ [1], a value comparable to that of barrierless alkali metal atom - dimer systems. It is found that the rate coefficient remains largely constant in the astrophysically relevant temperature range 10 -- 39~K [2], in agreement with the conclusions of a recent experimental study [3]. Implications of our findings to oxygen chemistry in the interstellar medium are discussed.\\ References: [1] Qu\'em\'ener et al., arXiv:0811.4377v1 (accepted in Phys. Rev. A); [2] G. Qu\'em\'ener, N. Balakrishnan, and B. K. Kendrick, J. Chem. Phys. {\bf 129}, 224309 (2008); [3] Carty et al., J. Phys. Chem. A {\bf 110}, 3101 (2006).