The first correlation functions from a neutron-light-charged-particle small-angle coincidence measurement are reported for the ,6 0+ 27 Al reaction at £( l6 0)=215 MeV. Clear evidence for singletdeuteron and 5 He production, and an anticorrelation of low-relative-momentum neutron-deuteron pairs, is observed. The nuclear temperature of 1.6 ±0.3 MeV, calculated from the ratio of excited-state to ground-state deuteron emission and corrected for sequential emission, is considerably lower than expected.PACS numbers: 25.70.GhIn recent years, two-particle correlation data at small relative momenta have been used to probe properties of nuclear interactions such as source sizes, 1 temperatures, 2 and decay lifetimes. 3 " 5 Correlations resulting from interactions between the two emitted particles can arise from several sources, including nuclear and Coulomb final-state interactions, 6 decays of particle-unstable states, 7 and quantum statistics. 8 We report here on correlation functions measured in the first two-particle interferometry experiment involving neutron-lightcharged-particle pairs, for which Coulomb interactions are absent. One principal motivation for this experiment was to test the "deuteron thermometer," 9 the simplest of the quantum thermometers which register the temperature of nuclear systems in terms of the population ratio of excited states of thermally emitted particles. Measurements of this kind have been made for relatively long-lived, y-emitting final states, 10 and also for particle-unbound states of complex fragments. 2 The deuteron thermometer is, however, particularly simple since the deuteron possesses only one excited state. It can also be utilized at lower energies where the thermal emission of more complex fragments is improbable, and where the reaction mechanism is more likely to involve the formation of an equilibrated compound nucleus. We will present np, nd, and na correlation functions, the production cross sections for excited-state deuterons id*) and 5 He fragments, and the nuclear temperature deduced from the deuteron thermometer.The experiment was performed using a 215-MeV 16 0 beam from the ATLAS accelerator at Argonne National Laboratory incident on a 800-jig/cm 2 target of 27 A1. This reaction was selected since the equivalent chargedparticle correlation data already exist. 5 Coincident particles were detected in two detector arrays centered at ±45° with respect to the beam and covering the angular range from 42° to 48°. Each array consisted of three Nal(Tl) charged-particle detectors in the horizontal plane, and four liquid-scintillator neutron detectors, two above and two below the horizontal plane. The opening angle between nearest neutron-charged-particle detector pairs was 3.1°. The six charged-particle detectors, 5.0-cm-diameter-by-3.8-cm-long cylindrical Nal(Tl) crystals covered with protective 6-mg/cm 2 Havar foils and coupled to phototubes, were placed 1.2 m from the target and collimated to a diameter of 3.8 cm. Chargedparticle identification was accomplished off line u...
