X-ray scattering study of the critical exponent η in argon

A new technique for evaluating the critical exponent η, which governs the rate of decay of the pair-correlation function with distance at the critical temperature, is described. In this method, η is obtained from plots of the reciprocal of the intensity as a function of the square of the scattering angle in the inner part of the small-angle scattering curve. The new procedure has the advantage of making use of the data at scattering angles at which the intensity is relatively high and thus is quite insensitive to effects which may distort the scattering curves. For argon, the value η=0.03±0.02 is obtained. The analysis of the scattering data also provides evidence for the need for corrections to the limiting scaling behavior which fluids exhibit very near the critical point.