Liquid hydrogen is a dense Bose fluid whose equilibrium properties are both calculable from first principles using various theoretical approaches and of interest for the understanding of a wide range of questions in many-body physics. . . .

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Published in Physical Review B: Condensed Matter and Materials Physics, v. 91, no. 18, article 180301, p. 1-6.

©2015 American Physical Society

The copyright holder has granted permission for posting the article here.

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We gratefully acknowledge the support of the US Department of Energy Office of Nuclear Physics (including Grant No. DE-FG02-03ER41258), the National Science Foundation (including Grants No. PHY-1068712 and No. PHY-1205833), PAPIIT-UNAM (Grant No. IN111913), and the Indiana University Center for Spacetime Symmetries.

Fig. 1.png (57 kB)
Fig. 1: Parahydrogen and orthohydrogen scattering cross sections at 20 K from ENDF-VII and the absorption cross section.

Fig. 2.png (27 kB)
Fig. 2: Experimental setup showing the cesium iodide detector array, liquid hydrogen target, and beam monitors.

Fig. 3.png (60 kB)
Fig. 3: Diagram of circulation loop inside the hydrogen target system. Evaporated hydrogen is recondensed and is forced to flow through the OPC at a rate of a few millimoles per second. T3, T7, T8, and T10 determine the liquid hydrogen bulk temperature. T2 and T5 determine the temperature of the catalyst in the OPC.

Fig. 4.png (51 kB)
Fig. 4: Observed ortho-para conversion over time as a fraction of the asymptotic limit for 3.42 meV neutrons shortly after filling the target, with a time constant of approximately one day. Residuals from the exponential fit are shown at the bottom.

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Fig. 5: Transmission monitor signals (left axis) for empty (triangles) and hydrogen-filled (squares) aluminum target vessel. Dips in the spectra are at the aluminum Bragg edges. Transmission ratio (right axis, diamonds) depicts no transmission for energies above 14.5 meV spin-flip transition.

Fig. 6.png (47 kB)
Fig. 6: Total cross section from this work in b/atom (triangles); parahydrogen scattering cross section (squares). The upper error bar on the parahydrogen cross section comes from Table I and the lower error bar is given by the upper limit on the orthohydrogen contamination.

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Fig. 7: The scattering cross section extracted in this work (triangles), Squires (diamonds), Celli (stars, some points omitted), Seiffert (circles), ENDF-VII (black), and subtraction of a 0.5% admixture of orthohydrogen from Seiffert (squares).

Table 1.GIF (38 kB)
Table 1: Main uncertainties in the total cross section at 1.92 meV.