Dynamic equation-of-state data for D2 and H2 were measured in the pressure range 2–76 GPa (20–760 kbar) using a two-state light-gas gun. Liquid specimens were shocked from initial states near the saturation curve at 20 K. Maximum compression was sixfold over initial liquid density at a calculated temperature of 7000 K for D2. The data is discussed in terms of the theory of Ross et al., which includes an effective intermolecular pair potential, molecular vibration, free molecular rotation, and molecular dissociation.

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Equation-of-state data were measured for liquid carbon dioxide and air shock-compressed to pressures in the range 28-71 GPa (280-710 kbar) using a two-stage light-gas gun. The experimental methods are described. The data indicate that shock-compressed liquid CO, decomposes at pressures above 34 GPa. Liquid air dissociates above a comparable shock pressure, as does liquid nitrogen. Theoretical intermolecular potentials are derived for CO, from the data. The calculated shock temperature for the onset of CO, decomposition is 4500 K at a volume of 17 cm3/mo1. ' 1. GPa = 10 kbar.

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Dynamic equation-of-state data for benzene, polybutene, and polyethylene were measured in the shock pressure range 19–210 GPa using a two-stage light-gas gun. Shock-front spectral luminosities were measured for benzene and polybutene using a fast five-channel optical pyrometer. The pressure–volume Hugoniot data above 20 GPa for benzene and polybutene are in agreement with both a statistical mechanics model and a Grüneisen model for shocked hydrocarbons decomposed into a two-phase mixture of carbon in a dense diamond-like phase and hydrogen in the condensed molecular phase. Published Hugoniot data of benzene up to 13 GPa are in good agreement with a model in which benzene retains its C6H6 molecular structure. The measured, effective, radiating temperatures of shock fronts in benzene are substantially lower than the temperatures calculated theoretically assuming thermal equilibrium. This substantial difference suggests that the measured, effective, radiating temperatures are not the chemical equilibrium temperatures behind the shock front for benzene and possibly for polybutene. Chemical equilibrium calculations which include up to 12 species suggest the presence of small concentrations of a few high-molecular-weight species in strongly shocked benzene and polybutene.

We report measurements of the specific heat of paramagnetic UA1 2 between 0.8 and 25 K in magnetic fields up to 43 kOe. A nearly field-independent T 3 lnT term dominates the temperature region below 10 K. The susceptibility was measured between 3 and 10 K and varies as 1-AT 2 . These results, and earlier resistivity measurements, are consistent with the predictions of the spin-fluctuation model. This is the first unambiguous observation of the specific heat predicted by the spin-fluctuation model for an atomic ally ordered paramagnet.Experimental verification of the existence of persistent spin fluctuations in exchange-enhanced paramagnets has been unsuccessful for the most part. In particular, the theoretically predicted contributions to the specific heat and magnetic susceptibility had never been unambiguously observed in any uniform metal prior to this work. 1 In this Letter we report low-temperature measurements of the specific heat and susceptibility of the narrow-band intermetallie compound UA1 2 which strongly support the theoretical calculations and indicate the presence of spin fluctuations associated with a narrow 5/ band. The existence of a low-temperature resistivity proportional to T 2 previously led to the proposal of spinfluctuation scattering in UA1 2 . 2 The spin-fluctuation modification of the electronic specific heat has been considered by a number of authors G Doniach and Engelsberg 3 and Berk and Schrieffer 4 have shown that the absorption and re-emission of spin fluctuations renormalizes the electronic self-energy, leading to an enhanced effective mass at low temperatures. This effect manifests itself as a low-temperature enhancement of the electronic specific-heat coefficient, y, which falls off with increasing temperature as T 3 ln(T/T SF ) for T«T SF . Here T S ?=T ¥ /S is the characteristic spin-fluctuation temperature, and T F and S are the degeneracy temperature of the band and the Stoner exchange-enhancement factor. Brinkman and Engelsberg 5 and BealMonod, Ma, and Fredkin 6 showed that this effect will be nearly insensitive to the presence of an external field.Exchange-enhanced pure metals, notably Pd, exhibit enhanced low-temperature values of y, but a spin-fluctuation contribution to the enhancement is difficult to separate from that due to the electron-phonon interaction, and quantitative comparisons with spin-fluctuation theory have been largely unsuccessful. The known spin-fluctuation system He 3 exhibits a T 3 lnT term in the specific heat at very low temperatures, 7 but such terms have not been observed in any metal prior to this worko 8 Very large exchange enhancements are found in some alloys near the critical concentration for ferromagnetism. Up turns in C/T for CttNi and RhNi have been fitted by T 3 InT terms and attributed to spin fluctuations. 9 ' 10 However, these effects are now known to be due to magnetic clustering (superparamagnetism)o 1,11 In the case of RhNi this was demonstrated by the observation that the upturn in C/T is suppressed by applied fields much smaller...

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