This new study of the vapor-phase infrared and Raman spectra of pdifluorobenzene (h,) and ( 4) includes assignments from the high-resolution electronic spectrum, from fluorescence spectra, and one assignment from the two photon electronic spectrum. A new set of frequencies and assignments has been made for the fundamentals of this important intermediate-sized molecule. The most important changes concern the assignments previously made for the lowfrequency a, mode (us), two members of the &, class (ui9 and YH)), and one very important change for the lowest frequency fundamental of the baU (out-of-plane) class (va), which has been observed directly in the far infrared. The results are all corroborated by the assignments of the perdeuterated analog where changes in previous assignments of Fermi resonance pairs have also been made. Some interesting differences between the Raman spectra of the vapor and the liquid perproto compounds have not been adequately explained in this study. 8 1985 Academic PRS. Inc.

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The potential scattering cross section for slow neutrons, a p , has, been measured for seventeen elements in order to determine the nuclear potential radius and to investigate the predictions of nuclear optical models. The measurements were based on total cross sections resulting from transmission experiments performed with the Brookhaven fast chopper. In the energy region where individual resonances can be resolved and their parameters determined with reasonable accuracy,

Matrix absorption and magnetic circular dichroism studies on 0s160, and OS'804 have been carried out to clarify the number of electronic transitions present in the region. The spectra show that the irregular vibrational structure in the I60 species with its onset at-276 nm is perfectly regular in the "0 compound. The system is, therefore, interpreted as a single electronic system analogous to that observed in the permanganate ion. The Raman spectrum of Os?O, single crystal has also been obtained.

and the elements in the Fe peak need temperatures well above 2X1G 9 °K for their formation. It is reasonable to suppose that the elements Na to Ca are produced at intermediate temperatures. We have shown that the carbon burning reactions at temperatures between 5X10 8 and 10X10 8 °K produce large amounts of Na 23 and of the Mg isotopes plus decreasing amounts of Al 27 and Si, but very little of heavier nuclei. One striking feature of our results is the relatively large ratio of Na 23 to Mg 24 produced, 1:2 to 1:5 depending on temperature, compared with the Suess-Urey 37 "cosmic abundance" ratio of 1:15. Our ratio of Mg 24 : Si 28 of about 50:1 is also in contrast with the cosmic abundance ratio of 1:1.