Inner bremsstrahlung-nuclear recoil angular correlation inK-capture

Abstract

It is suggested that a measurement of the inner bremsstrahlung (IB)-nuclear recoil angular correlation inK-capture leads to a method for determining the ratio |CA|2/|Cv|2, which is substantially free from dependence on either lifetime or spectral-shape factors, in contrast to the estimates of |CA|2/|Cv|2 made from theft values. So far a determination such as suggested here has been made only in the case of the β decay of aligned neutrons. In the case of7Be, the only known super-allowedK-capturer, a similar measurement might be of considerable interest since here some fairly dependable calculations of |MGT|, the Gamow-Teller matrix element, might be made. (Knowledge of |MGT| is essential in the evaluation of |CA|2/|CV|2). A general formula is derived for the IB-nuclear recoil angular correlation and applied to the particular case of the\(^7 Be\xrightarrow{{K - capture}}^7 Li\) β decay. In addition, it is shown that the formula, which in its general form assumes an initial (arbitrary) polarization for theK-capturing nucleus, offers the possibility of doing an unambiguous time-reversal experiment by looking for a left-right asymmetry in the count rate when polarization, recoil-momentum direction, and IB-direction are all mutually perpendicular.