LAUSR

Abstract In this study, we have determined the combined effect of pressure and temperature on the compressional-wave velocity (VP) of Ne up to 53 GPa and 1100 K using Brillouin scattering in externally heated diamond-anvil cells. The phase transition from the supercritical fluid to solid phase was observed to cause a 10.5–11% jump in VP, and the magnitude in the VP contrast across the phase transition increases with temperature. In addition, we have observed an abnormal reduced increase rate of VP with pressure in the supercritical Ne fluid at both 800 and 1100 K before the transition to the solid phase. VP of the solid Ne exhibits a nonlinear increase with pressure at all the investigated temperatures. The elevating temperature was noted to cause an apparent reduction in VP, yet the reduction in VP caused by increasing temperature dramatically decreases at higher pressures. At 20 GPa, increasing temperature by 100 K can lower the VP of Ne by 2.4%. Yet elevating temperature by 100 K can only reduce the VP by 0.4% at 50 GPa. We further compare VP of Ne to that of other rare gases, including Ar, Kr, and Xe. At 300 K, VP of Ne shows a stronger dependence on pressure than both Kr and Xe. Moreover, increasing temperature can produce a greater reduction in VP of Ne than that of Ar below 50 GPa. Our measured VP of Ne is also useful for understanding the velocity structure of giant planets, such as Jupiter.