,

reaction in the energy range considered (6.4-8.7 MeV) excites, altogether, 42 states, compared to a total of eight (d,p) transitions in the corresponding 49 Ti range (0-2.3 MeV).If the DW calculations are extrapolated from the bound to the unbound region, keeping the bound-state wave function fixed near zero binding, the estimated ( 3 He,d) strengths of the two 1=1 transitions to the analog states (levels 76 and 82) are «0.4 and -0.15, respectively. The corresponding AS Ti(d,p) strengths divided by (2T+1) = 5 are 0.5 and 0.12, respectively. ACKNOWLEDGMENTSThe authors wish to thank Professor R. Middleton and Professor W. E. Stephens for their continued interest in this work. It is a pleasure to acknowledge the help of Dr. R. H. Bassel in performing part of the distorted-wave analysis, and also P. Neogy, who assisted with the data analysis. The excellent service rendered by the NEUCC computing centre in Lundtofte, Denmark is greatly appreciated. The scanning of the nuclear emulsions was carefully performed by Mrs. M. Scrinivasan and Mrs. C. Coliukus. emulsions, bubble chambers, mass spectrometry, and radiochemistry. The last two methods have been used to measure product cross sections from the reaction of GeV protons with various targets. 3-7 However, no complete 3 Formation cross sections have been measured of about 60 radionuclides isolated from Ag irradiated by 3and 29-GeV protons. From these data, isobaric charge distributions and mass-yield curves were derived. At 3 GeV, the total isobaric cross sections are ^40 mb near the target, and they decrease to a broad minimum of 4 mb at around A = 30-40. For lighter products the cross sections increase again. At 29 GeV, light-and intermediate-mass products (20 65) have 10-20% lower yields. Corresponding charge-distribution curves at the two energies are identical except for shifts in absolute magnitude. Comparison of the 3-GeV mass-yield curve with the results of a Monte Carlo calculation based on a cascade-evaporation model shows that such a mechanism can account for the observed cross sections down to about mass 50. The lower-mass products (15<^4<35) must be formed mainly in a fragmentation or "fission-like" process. Comparisons are made with previous nuclear-emulsion and radiochemical results.

X mass spectronletric study of the relative yields of the strontiun~, yttriunl, zirconium, and 111olybdenum isotopes formed in the thernlal neutron fission of U235 has made possible a detailed examination of structure of the light mass region of the mass-yield curve. The relative yields of this work have been normalized t o 5.777'0 for Sr", and when literature and extrapolated values are talcen for the remaining chains, the fission yields total 100.87'0. IKTRODUCTIOKThere have been illany illass spectroilletric studies of the light illass fragments from the thermal neutron fission of UC3j. Tlle relative yields of the lcrypton isotopes mere first measured by Thode and Grahain (1947) and again by Wanless and Thode (1055). Glendenin et al. (1931) reported the relative yields of the zirconium, 111015 bdenum, and ruthenium isotopes; and Wiles et al. (1953) measured the relative yields of the rubidium and strontium isotopes. The first absolute cun~ulative yields for the light illass frag~nents using a illass spectrometer with the isotope dilution technique were reported by Petruska, Thocle, ancl Tomlinson (1953b). These authors normalized the relative yields of zirconium and nlolybdenunl reported b) Glendenin et al. (1951) to their absolute yielcls of strontium, rubidiunl, and Icrypton so that the total for the light mass group, including some estrapolatecl values, was 100%. Steinberg and Glendenin (1956) using the isotope dilution technique obtained absolute yields for strontium, zirconium, and molj bdenun~ which, together with relative yields for liryptoll and ruthenium and some radiochemical yields, were also forced to total 100%. Recent compilations of fission yields by I

Mass spectrometric analysis of cesium, barium, cerium, neodymium, and samarium produced in the thermal fission of Pu239 has made possible the determination of the cumulative yields of 17 mass chains. With previously published mass spectrometric yields of four xenon isotopes normalized to the present data a total of 21 cumulative yields are reported.

The effective neutron absorption cross section of Xe135 has been measured with a mass spectrometer by observing the variation in the Cs135/Cs137 fission yield ratio obtained at various thermal neutron fluxes. Values of 3.15 ± 0.06 megabarns and 3.27 ± 0.11 megabarns have been determined for neutron temperatures of 120 °C and 137 °C respectively.