Absolute Voltage Determination of Two Nuclear Resonances below 0.4 Mev

An absolute voltage determination was made of the ${\mathrm{F}}^{19}(p{\alpha }^{\prime },\gamma )$ and the ${\mathrm{B}}^{11}(p,\alpha )$ and ${\mathrm{B}}^{11}(p,\gamma )$ resonances. A calibrated electrostatic analyzer was used to measure the proton beam energy from a Crockroft-Walton linear accelerator. The values obtained were 0.3404±0.0004 Mev and 0.1628±0.0002 Mev, respectively. An approximate estimate of the half-width appears to give 2.0±1.0 kv for the fluorine and 4.5±1.5 kv for the boron resonance.