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1. He'(m m)He': E""=0. 95 (center of mass); mass defect = 12.92~0.05. 2. Li'(1 o)Hes: He'=He'+v+0. 97+0.05; mass defect = 12.94~0.05. 3. Li'(d He')He'. Qs --0.91&0. 09;mass defect= 12.85 0.09. 4. Li'(d o)He'. Qs --14.23&0.07; mass defect= 12.85 0.07. We adopt: He' mass defect=12. 92&0.08 Mev. I. (a) H'(d n)He4 Q =17.577 Zs 16. 63--(b) H'(1 e)He4The yield exhibits a pronounced maximum near E~=107 kev, with a cross section of 4.95&0.14 b (Ar 54) t Lsee also (Aj 52c)). Precise cross sections in the tange 8&=10 to 1700 kev are tabulated by (Ar 52d), ' E. P. Wigner and L. Eisenbud, Phys. Rev. 72, 29 (1947); T.Teichmann and E. P. Wigner, Phys. Rev. 87, 123 (1952).f' References are indicated by the erst two letters of the 6rst named author and are listed at the end of the article. VIII. Li6(y t)He' Q = -15.786 This reaction has not been observed with 17.6-Mev gammas. The cross section is &6&4pb (Ti 54b). Ix. Li~(e g')Li6 See Li'. Li'(e e')Li'. X. (a) Li'(p p')Li'* (b) Li'(d d')Li'* Proton and deuteron groups are observed corresponding to the state at 2.19 Mev. At Eq= 7.4 Mev (|I = 90'), no deuteron group corresponding to the presumed T= 1 state at 3.57 Mev is observed [(Br53h) and C. P. Browne, private communication). See also (Aj 52c). ENERGY LEVELS OF LIGHT NUCLEI Lie, Be6 He7, Li7XI. Li'(p d)Li' Q"= -5.010Deuteron groups have been observed corresponding to the ground state, and to levels at 2.2&0.2 and 3.7 &0.2 Mev (Fr 52). At E"=18 Mev, angular distributions of the deuterons to the ground state and the 2.19-Mev level, analyzed by pickup theory, indicate l"=1 and hence even parity, 7 &3, for both states (Re 54a).XII. Li'(d t)Li' Q = -0.988The angular distributions of the tritons, analyzed by pickup theory, indicates l"=1, and hence even parity for the ground state (Ho 53c, Le 54) and for the 2.19-Mev state (Le 54). At Eq 14.5 M-ev, the cross sections Ka

43the result is admittedly very approximate, it does show that from the state 7=2 the predominant process is neutron absorption.The number given for the mesic absorption probability also represents absorption from the 7=0 state and is much smaller than the neutron probability. For states of higher /, additional powers of the meson and nucleon momenta appear which make the probability for mesic absorption extremely small. We may, therefore, say that no neutral mesons should be observed, regardless of their parity. IV. CONCLUSIONSPreliminary results of the experiment of Panofsky, Aamodt, and Hadley on the absorption of ir~ mesons in deuterium 14 indicate a gamma-ray spectrum with a large peak in the neighborhood of 130 Mev, w r hile there is no detectable peak in the spectrum at 70 Mev where the decay quanta from the neutral meson would appear.

Previous measurements on the Be 9 (d,w)B 10 neutron spectrum at 0° and 80° have been extended to 10°, 30°, and 45° to check the energy level assignments and to deduce the parity of the levels from a Butler analysis of the angular distributions. The observed neutron groups correspond to levels of B 10 at 0. 72, 1.75, 2.15, 3.53, 4.78, 5.14 (doublet), 5.37 (?), 5.58, 5.72 (?), 5.93, 6.12 (possibly doublet), 6.38, 6.58, and 6.77 Mev. The estimated uncertainty is 0.06 Mev for the first five states of B 10 and 0.04 Mev for the higher energy levels. The Butler analysis of the angular distribution data indicates that the ground state and the first four excited states of B 10 are of even parity and that both components of the 5.14-Mev doublet are probably odd parity states. Parity assignments for some of the other energy levels have been attempted. The spins of these states cannot be uniquely determined on the basis of the Butler analysis, but the possible spin limits are listed. A Be 9 (d,p)Be 10 exposure was also made. There do not appear to be any states in Be 10 between the ground state and the known 3.37-Mev level.work to the angular distributions of neutrons resulting from the deuteron bombardment of Be 9 .EXPERIMENTAL PROCEDURES-(<*,n) EXPOSURE Deuterons from the Wisconsin electrostatic generator, after passing through the 1-meter cylindrical analyzer and a f-inch defining aperture in 0.01-inch tantalum, struck a thin Be 9 metallic target 3 mounted on a tantalum backing. The average deuteron energy was 3.39 Mev. The resulting neutrons were observed by means of NTA (Eastman-Kpdak) emulsions, 200 microns thick, mounted 10 centimeters from the target, and at angles of 0°, 10°, 30°, 45°, and 80° to the incident beam.The following processing technique, suggested by Mrs. M. J. Wilson Laubenstein, was employed: The plates, supported in a Lucite holder, were immersed in a solution of 1 part D-19 and 1 part distilled water. This solution was at 5 °C* After 30 minutes, 4 parts of distilled water at room temperature (approximately 22 °C) were added. The plates remained in this mixture of 1 part D-19 to 5 parts distilled water for 30 minutes, and were then placed in a solution of 1.5 percent acetic acid at 5°C for another thirty minutes. After this stopping treatment, the plates were transferred to a hypo solution (30 percent sodium hyposulfite by weight, 70 percent distilled water) for a length of time 1.5 times the period necessary for clearing the emulsion. The plates were then washed in running water for about 6 hours, dipped in a solution of 50 percent ethyl alcohol and 50 percent water for a couple of minutes, and then allowed to dry in a reasonably dust-free room.The acceptance criteria that were applied to the proton recoil tracks are similar to the ones discussed in a paper by Johnson, Laubenstein, and Richards. 4 The range-energy relation used to compute the energy of 3 The foil was kindly furnished by Dr. Hugh Bradner. Its thickness corresponds to a stopping power of approximately 50 kev for deuterons of 3.5 Mev. ...

This work was sponsored by the AEC. 1 J. Steinberger, W. Panofsky, and J. Steller, Phys. Rev. 78, 802 (1950). 2 K. Brueckner, Phys. Rev., in press. His calculations of radiative corrections did not include effects from virtual neutral mesons, but it does not seem that this would change his results in a qualitative manner.3