Shrinkage correction

Knife-edges may also be used in this case as a basis for film-shrinkage corrections. 

The unsymmetrical, or Straumanis, method of film loading is shown in Fig. 6-5(c) and Fig. 3-12. Two holes are punched in the film so that it may be slipped over both the entrance collimator and the beam stop. Since it is possible to determine from measurements on the film where the incident beam entered the film circle and where the transmitted beam left it, no knife-edges are required to make the film-shrinkage correction. The point X (20 = 180°), where the incident beam entered, is halfway between the measured positions of lines 4,4 similarly, the point Y (20 = 0°), where the transmitted beam left, is halfway between lines 1,1. The difference between the positions of X and Y gives W, and 0 is found by proportion ... 

Unsymmetrical loading thus provides for the film-shrinkage correction without calibration of the camera or knowledge of any camera dimension. It is the most popular film arrangement. 

Shrinkage correction assumed equal to that of fenocene. Not corrected for shrinkage. 

The microwave experiments indicate a linear configuration of the SiN=C=X groups in the ground vibrational state. Shrinkage corrections improve the agreement between electron-diffraction and microwave data. 

An analysis without consideration of shrinkage corrections such as pseudorotation gave the best fit to the experimental data when Civ symmetry was assumed. 

There is no modern structural information for silicon tetraiodide, so its structure has now been determined by electron diffraction at 378 K. " It is, of course, regularly tetrahedral, and the Si-I bond distance (rg) was determined to be 243.2(5) pm. The non-bonded T T distance refined to 397.1(8) pm. These two distances indicate that there is a very small shrinkage correction in this case. 

Thermometer Bulb Shrinkage Correction— Apply the correction for shrinkage of the mercury bulb of the thermometer as determined by any change in its ice or steam point where applicable. Other means can be employed, such as the use of a platinum-resistance thermometer or a National Bureau of Standards thermometer. 

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