Specific heat of quench-condensed hydrogen films

Journal Article · Wed May 01 04:00:00 EDT 1996 · Journal of Low Temperature Physics

DOI:https://doi.org/10.1007/BF00755976· OSTI ID:283046

Birmingham, J T; Richards, P L ^[1]; Meyer, H ^[2]

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1. Univ. of California, Berkeley, CA (United States)
2. Duke Univ., Durham, NC (United States)

The specific heat C(X,T) of quench-condensed films of H{sub 2} has been measured as a function of ortho concentration X with 0.28 2.5 K, there is a peak which indicates a bulk-like ordering transition. At temperatures below the peak, there is a large contribution to C, which is not present in bulk H{sub 2}, and which the authors attribute to short-range ordering size effects. As T{sub cond} is decreased below 2.5 K, the shape of the specific heat curve changes, and the peak at 1.5 K is replaced by a gradual rise with a sharp drop above 2.6 K. Despite this strong dependence of C on T{sub cond}, the entropy per molecule at 3 K is only weakly dependent on T{sub cond} and comparable to that for bulk H{sub 2}. Film annealing at 3.4 K produces a change in the specific heat curve, and a study of this effect is presented. The ortho-para conversion rate of the films condensed at the various temperatures is found to be same as in bulk, well-annealed H{sub 2}. As in bulk H{sub 2}, the transition temperature inferred from the location of the specific heat peak or anomaly decreases with X. Unlike in bulk H{sub 2}, there is no temperature hysteresis in C for any of the quench-condensed films. This implies that the ordering transitions are not accompanied by a martensitic transformation.

• Sponsoring Organization: USDOE
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 283046
• Journal Information: Journal of Low Temperature Physics, Journal Name: Journal of Low Temperature Physics Journal Issue: 3-4 Vol. 103; ISSN JLTPAC; ISSN 0022-2291
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
HYDROGEN
PHASE TRANSFORMATIONS
SPECIFIC HEAT
TEMPERATURE RANGE 0000-0013 K
THIN FILMS