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The structure of liquid argon as determined by x-ray diffraction


Kirstein, Bruce Edward (1972) The structure of liquid argon as determined by x-ray diffraction. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/88K0-V473.


X-ray diffraction measurements and subsequent data analyses have been carried out on liquid argon at five states in the density range of 0.91 to 1.135 gm/cc and temperature range of 127 to 143°K. Duplicate measurements were made on all states. These data yielded radial distribution and direct correlation functions which were then used to compute the pair potential using the Percus-Yevick equation. The potential minima are in the range of -105 to -120°K and appear to substantiate current theoretical estimates of the effective pair potential in the presence of a weak three-body force.

The data analysis procedure used was new and does not distinguish between the coherent and incoherent absorption factors for the cell scattering which were essentially equal. With this simplification, the argon scattering estimate was compared to the gas scattering estimate on the laboratory frame of reference and the two estimates coincided, indicating the data normalized. The argon scattering on the laboratory frame of reference was examined for the existence of the peaks in the structure factor and the existence of an observable third peak was considered doubtful.

Numerical studies of the effect of truncation, normalization, the subsidiary peak phenomenon in the radial distribution function, uncertainties in the low angle data relative to errors in the direct correlation function and the distortion phenomenon are presented.

The distortion phenomenon for this experiment explains why the Mikolaj-Pings argon data yielded pair potential well depths from the Percus-Yevick equation that were too shallow and an apparent slope with respect to density that was too steep compared to theoretical estimates.

The data presented for each measurement are: empty cell and cell plus argon intensity, absorption factors, argon intensity, smoothed argon intensity, smoothed argon intensity corrected for distortion, structure factor, radial distribution function, direct correlation function and the pair potential from the Percus-Yevick equation.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Chemical Engineering
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Pings, Cornelius J.
Thesis Committee:
  • Unknown, Unknown
Defense Date:25 May 1972
Funding AgencyGrant Number
Air Force Office of Scientific ResearchUNSPECIFIED
Record Number:CaltechTHESIS:04292016-140637476
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9691
Deposited On:02 May 2016 16:20
Last Modified:09 Nov 2022 19:20

Thesis Files

PDF (Kirstein Part I) - Final Version
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PDF (Kirstein Part II) - Final Version
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PDF (Kirstein Part III) - Final Version
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