FIG. 15. The photo-line of K 40 and Na 24 and Co 60 calibration lines. The source strength was less than 10~9 curie. The data were taken in about five hours. The K 40 energy is 1.48±0.02 Mev. 40 50 60 70 80 90 KX) PULSE HEIGHT(VOLTS)of the pulses in K 40 show that there is no other gammaray present with an intensity greater than about 10 percent of the 1.48-Mev line. Our success with the photographs of oscilloscope patterns suggests that this technique will be valuable for work with weak sources since it serves the purpose of a multichannel discriminator. Densitometer traces we have made of gamma-ray patterns resemble the discriminator curves very closely. For initial spotting of gamma-ray lines this technique will probably not be surpassed.We are greatly indebted to Drs. Dean Cowie and P. Abelson of the Carnegie Institution of Washington for supplying us with sources of Ga 66 . We wish to thank Drs. E. P. Tomlinson and J. L. Simons for sources of Au 198 .Photo-neutron yields from spheres of D 2 0 and Be containing Na 24 and Ga 72 gamma-ray sources were measured by spatial integration of induced foil activities in a large paraffin block. A standard neutron source was used to calibrate the apparatus.The Ga 72 and Na 24 sources were subsequently dissolved, and their radioactive strengths were measured by beta-counting of aliquots. The data so obtained, when combined with the known wall thickness of the spheres led to the following results after the application of appropriate corrections:(1) Photo-disintegration cross section of D at 2.76 Mev: 14.3X10~2 8 cm 2 (2) Photo-disintegration cross section of Be at 2.76 Mev: 6.74X10 -28 cm 2 (3) Cross section of D at 2.50 Mev multiplied by intensity of 2.50 Mev line in quanta per Ga 72 beta-emission: 2.81 X10-28 cm 2 (4) Sum of cross sections of Be at 1.84, 2.20 and 2.50 Mev weighted according to respective gamma-intensities in Ga 72 : 2.16 X10~2 8 cm 2These results are believed accurate within 8 percent. Agreement with theory is discussed for both D and Be.
Metastable transitions were studied in the mass spectra of methanol and deuterated methanols in a sector mass spectrometer. The relative abundances of the various metastable ions at 70eV were determined. The intensities are in good agreement with those obtained employing a double‐focussing instrument operating in the metastable mode. There is a strong isotope effect on the intensity of the anomalous parent‐ion metastable transition. This transition and the one leading to a “flat top” metastable peak were studied carefully. Appearance potentials were determined for the ions involved, by the RPD method and for the metastables themselves by conventional techniques. Metastable ion decay curves were obtained using an improved pulsed ion source. The results are discussed in terms of the quasi‐equilibrium theory of mass spectra.
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