Improved temperature dependence of rate coefficients for rotational state-to-state transitions in H$_{2}$O + H$_{2}$O collisions

Abstract

Aim: We present an improved database of temperature dependent rate coefficients for rotational state-to-state transitions in H$_{2}$O + H$_{2}$O collisions. The database includes 231 transitions between the lower $para$- and 210 transitions between the lower $ortho$-states of H$_{2}$O (up to $j=7$) and can be employed for cometary and planetary applications up to the temperature of 1000 K. Methods: New general method is developed and applied which permits to generate rate coefficients for excitation and quenching processes that automatically satisfy the principle of microscopic reversibility and, also, helps to cover the range of low collision energies by interpolation of cross sections between the process threshold and the computed data points. Results: It is found that in the range of intermediate temperatures, $150 < T < 600$ K, new rate coefficients are in good agreement with those reported earlier, but for higher temperatures, $600 < T < 1000$ K, the new revised temperature dependence is recommended. The low temperature range, $5 < T < 150$ K, is now covered, by the abovementioned interpolation of cross sections down to the process threshold.