Possible Negative Value of the Gruneisen Coefficient of Hydrogen in the Pressure Range from 40 to 75 GPa and Temperature Range from 3500 to 7500 K
A. B. Medvedev1,2
1Institute of Experimental Physic, Sarov, 607188 Russia
2Sarov Institute of Physics and Technology, Sarov, 607186 Russia
Keywords: водород, протий, дейтерий, уравнение состояния, давление, температура, плотность, энергия, коэффициент Грюнайзена, ударная адиабата, изоэнтропа, конвекция, Юпитер, hydrogen, protium, deuterium, equation of state, pressure, temperature, density, energy, Gruneisen coefficient, shock adiabat, isentrope, convection, Jupiter
Abstract
Experimental data on single and double shock compression of initially liquid and gaseous (compressed by initial pressure) hydrogen isotopes (protium and deuterium) at pressures of ≈10-180 GPa and temperatures of ≈ 3000-20000 K are considered. The mean values of the measured variables (pressure, density, internal energy, and temperature) show that hydrogen at a pressure of ≈ 41 GPa in the temperature interval of ≈ 3500-5700 K and at a pressure of ≈74 GPa in the temperature interval of ≈5000-7500 K is characterized by a negative value of the Gruneisen coefficient. Such an anomaly may play a key role in some processes, including those proceeding in the Jupiter gas shell, which mainly consists of protium (≈ 90%) and helium (≈ 10%). In the range of pressures (depths) of its manifestation, convection in the protium shell is forbidden with an increase in temperature in the shell with increasing pressure. Possibly, a comparatively moderate fraction of helium does not suppress the anomaly, and it serves as a barrier for large-scale convection in the Jupiter shell. Experiments are required to confirm this anomaly.
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