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Two-photon excitation enabled for the first time the observation and measurement of excited state fluorescence lifetimes from three flavanols in solution, which were ~ 1.0 ns for catechin and epicatechin, but <45 ps for epigallocatechin gallate (EGCG). The shorter

From a recent experiment in this laboratory (Shute et al. 1962) on the elastic scattering of protons from 12C, resonance levels (E13N, J1t) of 13N were obtained at the laboratory bombarding energies (Ep) shown in Table 1. To confirm these results, an investigation of the yield and angular distribution of gamma rays from the reaction 12C(p'YO)13N and 12C(p'Yl)13N was undertaken. Accordingly, the theoretical angular distributions, W(8), for the gamma ray (Yo) to the ground state of 13Na-) and also for the gamma ray (Yl) to the 1st excited state of 13Na+) were evaluated on the assumptions that overlap of levels in 13N is small and lowest order multipoles are involved. As angular distributions are parity insensitive, these were found to be identical for the two gamma rays expected. The simpler of these angular distributions are also shown on the table. The expected angular distributions indicate that 90° is a suitable angle for yield curves.

SummaryThe 90° yields of y·rays from the reaction 27Al(p,y)28Si have been obtained at intervals of 40 ke V for proton energies between 8·02 and 10·42 MeV. The ground state y-ray (Yo) and the first excited state y-ray (Yl) were adequately resolved. The two yield curves show considerable structure and, with the present resolution, there is a strong one-way correspondence between them. The gross structure of the Yo yield curve is compared with data from the 28Si( y,n)27Si reaction and fair agreement is found.

Measurements of the angular correlation between the two a particles emitted in the reaction 16 0(a,2a) 12 C g . s . at incident energies near 25 MeV suggest that this reaction can be described in terms of both sequential and one-step knockout processes. The sequential reaction proceeds as inelastic a-particle scattering followed by a-particle decay of the excited levels of 16 0 to levels of 12 C. Only the transitions to the ground state of 12 C were studied. The most strongly excited levels were those at 11.1 and 13.88 MeV. The strong energy dependence of the cross section for the reaction going through the 13.88-MeV level indicates the existence of a broad state in 20 Ne with an excitation energy near 24 MeV. Apparently, resonance effects are present in the initial-state interaction at this excitation. Any quasi-elastic scattering appears as a background under the peaks of the sequential reaction. The angular distribution of this background is in limited agreement with the predictions of a modified Born-approximation model which takes into account the final-state interaction between the two a particles.