To: Professor Pauling

From: R. A. Pasternak and L. Katz

Subject: Photographs of Muscle by Lotmar and Picken

Some of the photographs of Lotmar and Picken were remeasured using reproductions of the originals. No details wore lost by this procedure.

Zero Layer Reflections

The intense film No. 1 was measured by both Pasternak and Katz, the somewhat weaker film No. 7 by Pasternak as an additional check.

The sanple-to-film distance was found from the two NaCl powder lines appearing on the films. As the lines are rather diffuse, a reliability of only about ± 1% could be obtained.

Zero layer reflections are quite sharp on these two films, though on other films some of them are double. However, they are not always symmetrical in position and intensity about the origin. We estimate that errors in the calculated spacings ranging from ± 0.1 A for the longer spacings to ± 0.05 A for the shorter ones are possible. Our results are summarized in table 1 and compared with those of Lotmar and Picken.

Our measurements differ from those of L. and P. in the following particulars:

(1) We observed very weak but distinct reflections, A₃ and A’₃, whereas L. and P. report only one doubtful line, A₃.

(2) A’₄, A”₄, A’₇, A’₉ are not reported by L. and P.; we too consider the first three to be somewhat doubtful as they seem to be above the Zero layer line.

3) A₁₀ seems to be doubtful, although L. and P. also report one line in this range.

(4) We observe A₈ to be of medium intensity, whereas L. and P. report it as questionable.

First Layer Reflections

Photograph No. 1 was measured by both of us, photograph No. 3 by one of us (P) as an additional check. The four quadrants of the photographs are not identical, but since the photographs exhibit nearly twofold symmetry, measurements for quadrants 1 and 3, and for 2 and 4, are reported together.

We determined the position of each reflection by measuring its polar coordinates, distance being measured from the direct beam spot and angle being measured from the equator. Whereas the distance from the center is fairly well defined, though less reliable than for the zero layer, the angle can be measured only very approximately due to the arcing of the reflections. Our results are summarized in table 2. The comparison of our spacings with those of L. and P. has limited value, as these authors did not indicate what photographs and which quadrants they measured.

Layer Line Spacing

In Fig. 1 we have plotted the ends of the radius vectors for the reflections. Symmetry was obtained by mirroring the plot through the vertical axis, y. The smooth curve was then drawn so that the plotted points were approximately evenly distributed about it with no attempt to weight the points. The intercept of this curve with the vertical axis represents an axial spacing of 5.11 A.; the spread of the points is such as to indicate a possible error of about ±0.3 A. The spacing of 5.11 A. was then used for calculating the first layer line hyperbola (crosses in Fig. l). It practically coincides with the interpolated curve derived from the observed reflections. The hyperbola calculated for the axial spacing of 5.65A, as reported by L. and P. (circles in Fig. 1) does not fit our measurements since it lies entirely too low.

In his seminar at Cal. Tech., Bamford quoted an identity, distance of 5.34A which he had calculated from the position of the innermost first layer reflection alone. His method of calculation gives all the weight to one reflection and ignores all the others, several of which are as well defined as the first. We therefore feel that his value has less significance than ours.

General Reflections

Between the zero and first layer lines some indistinct maxima in the scattering can be observed. They are too badly defined to be measured or identified. Outside the first layer lines some weak reflections are present. Their positions are reported in table 3. These very weak reflections are rather long arcs and the angles are therefore only approximate.

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