Study of quantum diffusion in hydrogen using calorimetric methods

Dilute solid solutions of hydrogen with ortho-fractions of x=0.10, 0.2, 0.5 and 1.1 at.% have been investigated using two experimental procedures by means of an adiabatic calorimeter in the temperature range 0.4-3 K. One method employing the time dependence of the heat capacity was used to determine the characteristic times tau needed for the configuration equilibrium to set and the temperature dependence of the heat capacity of the ortho-subsystem such a distribution of clusters which is equilibrium at the temperature of the experiment and almost constant during a single measurement. The experimental results are compared with the rotational heat capacities calculated in the framework of a simple statistical model. A method of determine tau from the measured amount of the power releazed in solid hydrogen owing to both conversion and clusterization has been suggested and realized. From calorimetric result it follows that within the exprimental error, tau is concentration ndependent. The temperature dependence of tau at T < 1 K follows the law tau approximately T-1