The Central Temperature of the Sun can be Measured via the 7^7Be Solar Neutrino Line

A precise test of the theory of stellar evolution can be performed by measuring the difference in average energy between the neutrino line produced by ${\rm ^7Be}$ electron capture in the solar interior and the corresponding neutrino line produced in a terrestrial laboratory. The high temperatures in the center of the sun broaden the line asymmetrically, FWHM = 1.6~keV, and cause an average energy shift of 1.3~keV. The width of the $^7$Be neutrino line should be taken into account in calculations of vacuum neutrino oscillations.Comment: RevTeX file, 9 pages. For hardcopy with figure, send to [email protected]. Institute for Advanced Study number AST 93/4

Isomer shift calibration of /sup 129/I and /sup 127/I by life-time variations in the electron-capture decay of /sup 123/I

The isomer shift of a Mossbauer isotope is proportional to the electronic density difference at the nucleus. The electron capture decay mode constant lambda is proportional to the electronic density at the nucleus. The authors performed direct measurements of Delta lambda for several pairs of iodine compounds labelled with /sup 123/I using differential ionisation chambers. The /sup 123/I activity was produced by /sup 127/I(p,5n)/sup 123/Xe decaying by electron capture to /sup 123/I.Anglai

Isomer shift calibration of /sup 57/Fe by life-time variations in the electron-capture decay of /sup 52/Fe

Electron densities at the nucleus are estimated from measurements of the change in electron capture rate of /sup 52/Fe in different iron compounds. This leads to a calibration constant alpha for the /sup 57/Fe isomer shift: alpha =-0.31+/-0.04 a/sub 0/ /sup 3/ mm s/sup -1/.Anglai