Continuum Resonances inHe4(p, p′He4

Abstract

Two resonances are seen in the spectrum of inelastic protons from ${\mathrm{He}}^4$ with 40-MeV protons incident upon a NTP helium gas target. Resonance I lies at an ${\mathrm{He}}^4$ excitation energy $E^{*}=20.46\mathrm{}\pm 0.14$ MeV and has a c.m. full width ${\Gamma }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=340\mathrm{}\pm 40$ keV, while II is at $E^{*}=22.00\mathrm{}\pm 0.14$ MeV with ${\Gamma }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=2.4\mathrm{}\pm 0.5$ MeV. Data were taken over the range $19\le E^{*}\le 24$ MeV at 11 lab angles, $15°\le \theta \le 90°$, with a 32-detector array of solid-state passing counters mounted in the focal plane of a double-focusing 180° magnetic spectrometer. Angular distributions for the two inelastic groups were obtained through a subtraction of tentative phase space and/or experimental backgrounds. Kinematic limitations prevented following a third broad resonance which appeared at $26\le E^{*}\le 28$ MeV.