A comparison of the energies of alpha particles from six different ${\mathrm{Po}}^{210}$ sources was made with the same broad-range spectrograph used for a recent comparison of the ${\mathrm{Po}}^{210}$ alpha-particle energy with the ${\mathrm{Li}}^7(p, n){\mathrm{Be}}^7$ threshold energy. The sources were prepared by different techniques and some were on flat backings whereas others were on cylindrical backings. It is concluded that the discrepancies in the most recent measurements of the alpha energy do not arise from source preparation techniques but the lower values of the older measurements may have been caused by source aging.

• Received 20 July 1961

DOI:https://doi.org/10.1103/PhysRev.124.1494