Dissociation of exciton states in warm dense hydrogen

The transition from the molecular state to the atomic state in warm dense hydrogen fluid has been actively studied in the past few decades. The use of various experimental techniques has not yet led to reliable results consistent with each other. Despite numerous attempts, theoretical methods have not yet explained existing discrepancies in the experimental data and the microscopic mechanism of the transition of hydrogen fluid to a conducting state. In [I.D. Fedorov, N.D. Orekhov, and V.V. Stegailov, Phys. Rev. B 101, 100101 (R) (2020)], the importance of taking into account nonequilibrium nonadiabatic processes in the analysis of the mechanisms of such transition was demonstrated. In this work, the characteristics of exciton states formed as a result of spontaneous vibronic excitations are calculated. It is shown that the dissociation of such excitons at high temperatures can explain the experimentally observed features of the transition under study.