A Search for Levels of 7Li Between 9·0 and 9·55 MeV Excitation

Abstract

SummaryThe cross section of the reaction 6Li(n,3H)'He has been measured, with good energy resolution, over the neutron range 2·0--2·65 MeV. This corresponds to an excitation of 7Li from 9· 0 to 9· 55 MeV, a region in which photodisintegration experiments indicate the presence of one or more levels. No resonance structure was observed in this experiment and possible reasons for this are discussed. Kern and Kreger 1958). These results show that, with the exception of the broad p-wave resonance at 255 keV, no resonance structure is apparent over the whole of the measured energy range. This is surprising as several fairly well-established levels are known to be present in the compound system, 7Li*. " In the experiments reported here, the cross section of 6Li(n,3H)4He was measured, with good energy resolution, over a neutron energy range 2 ·0-2 . 65 MeV; this corresponds to an excitation of the compound 7Li system from 9·0 to 9 ·55 MeV where a fairly well-established level of 7Li is known to be present (Ajzenberg and Lauritsen 1955). From a knowledge of the neutron and triton partial widths which have been established for this level by y-ray absorption experiments it would appear that, to an order of magnitude, the resonance cross section to this level by neutron absorption in 6Li should be several hundred millibarns. The experimental techniques used here were Sufficiently sensitive so that a 10 per cent. change in the cross-section curve having a 40 keV half-width should be readily detected.