Gamma-rays from proton capture in 26Mg

Gamma-rays produced by the resonance capture of 454 key protons in natural magnesium have been investigated with a scintillation spectrometer• This resonance has been assigned to the reaction 26Mg(p, V) 27A1 by T a n g e n 1), as the final nucleus emits no positrons. The resonant energy has been determined most accurately by Hunt and Jones2) as 454.2 4- 0.3 key. Natural magnesium exhibits many resonances 1)2) in the low energy region, of which the 454 key resonance is the most prominent one. Gamma-rays of energy EV = 4.9 and 6.2 Mev have been found from this resonance by Russell et al. 3) with an aluminum absorption method. The only scintillation spectrometer investigation of this reaction has been made by Casson 4)at the 338 and 314 kev resonances. At E# = 338key 7-rays of Ey = 2.83 i 0.14 and 5.80 4- 0.25 Mev and at 314 kev a 7-ray of E7 = 4.2 4- 0.2 Mev are observed

The infrared isotope analyzer II

The investigation of the new method for determining isotope ratios by infrared gas analysis has been continued. The amount of carbon dioxide required for a 13C/12C analysis has been reduced. The sensitivity is now 0.005 at.% excess 13C in 20 mg CO2 and 0.008 at.% excess 13C in 8 mg CO2. The method has been extended to the determination of the 15N/14N ratio in nitrous oxide (*NNO) and the sensitivity reached is 0.015 at.5% excess 15N in 6 mg N2O

An infrared isotope analyzer

The shift in the infrared absorption bands of isotopic molecules is used in a new method for determining the isotope ratios in tracer experiments. The infrared absorption is measured with a non-dispersive filter instrument containing as selective detector a gas cell filled with a concentrated sample of the component to be measured. An instrument is devised according to this method, to measure the 13C/12C ratio in carbon dioxide. It permits the measurement of the 13C abundance in 30 mg carbon dioxide with an error of 0.005 at.% in the neighbourhood of the natural abundance of 1.1 at.%. This precision is sufficient for the majority of tracer experiments. A more detailed account of this study is to be found in the thesis 5) of one of us

The infrared isotope analyzer II

The investigation of the new method for determining isotope ratios by infrared gas analysis has been continued. The amount of carbon dioxide required for a 13C/12C analysis has been reduced. The sensitivity is now 0.005 at.% excess 13C in 20 mg CO2 and 0.008 at.% excess 13C in 8 mg CO2. The method has been extended to the determination of the 15N/14N ratio in nitrous oxide (*NNO) and the sensitivity reached is 0.015 at.5% excess 15N in 6 mg N2O

The reaction 25Mg (p,[gamma]) 26Al (I experimental)

Energies and intensities have been measured of γ-rays produced in the 25Mg(p, γ)26Al reaction at six resonances in the region Ep = 0.3 − 0.7 MeV. Thin enriched 25Mg targets were bombarded with protons from a Cockroft-Walton generator, and γ-rays were detected with a scintillation spectrometer. The resulting pulse spectra were analyzed with a differential discriminator and photographed on an oscilloscope screen. The resonances investigated here could be assigned to 25Mg by comparison with runs on enriched 24Mg and 26Mg targets. The 25Mg resonances are found at 321, 395, 441, 501, 518, 580, 607, 667 and 688, all ± 15 keV. The 501 and 518 keV resonances could not be resolved completely, but they show almost identical γ-ray spectra. The resonances at 667 and 688 keV have not been investigated in detail. The six resonances investigated in detail show complicated γ-ray spectra, different from resonance to resonance. A list of γ-ray energies and intensities is given in Tables II and III. From absolute γ-ray yield measurements the radiation widths of all resonances (multiplied by a statistical factor) could be determined