Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 4 of 4
Full-Text Articles in Physical Sciences and Mathematics
Average Reaction Cross Sections For 74- To 112-Mev Α Particles On 127I And 133Cs, R. E. Warner, H. W. Wilschut, W. F. Rulla, Gary Felder
Average Reaction Cross Sections For 74- To 112-Mev Α Particles On 127I And 133Cs, R. E. Warner, H. W. Wilschut, W. F. Rulla, Gary Felder
Physics: Faculty Publications
The average reaction cross section for 74- to 112-MeV α particles on 127I and 133Cs was measured by a new method using a magnetic spectrograph and a CsI scintillation detector. The result, σR=2220±50 mb, is in good agreement with optical model calculations and finite-range microscopic calculations. Zero-range microscopic calculations underpredict σR by about 10%, while strong absorption theories overpredict σR by large amounts.
Microscopic Calculations Of Low-Energy Reaction Cross Sections, R. E. Warner, Gary Felder
Microscopic Calculations Of Low-Energy Reaction Cross Sections, R. E. Warner, Gary Felder
Physics: Faculty Publications
Microscopic calculations of nuclear reaction cross sections and total reaction probabilities are compared with measurements for the d+Si, 3,4He+Si, and d+Ge systems at energies ranging from 2 to 53 MeV/nucleon. Good agreement is obtained, except for 3He+Si at the very lowest energies, when zero-range nucleon-nucleon forces are assumed and realistic nuclear density distributions are used in the tail regions, where the models are most sensitive. The agreement is less good for finite-range forces. A strong absorption model gives much poorer agreement with the recent 4He+Si measurements than do the microscopic models.
Spectroscopic Limits On High-Redshift Lyα Emission, James D. Lowenthal, Craig J. Hogan, Robert W. Leach, Gary D. Schmidt, Craig B. Foltz
Spectroscopic Limits On High-Redshift Lyα Emission, James D. Lowenthal, Craig J. Hogan, Robert W. Leach, Gary D. Schmidt, Craig B. Foltz
Astronomy: Faculty Publications
We have conducted a deep long-slit spectroscopic search for high-redshift (2.7 < z < 4.7) Lyα emission. Four pairs of deep, high-resolution (R ≈ 2000), long-slit CCD frames were taken at the Multiple Mirror Telescope. The "blank sky" in each pair of frames was searched for faint emission features unresolved spatially and spectrally. No emission features were found down to a limiting line surface brightness (1 σ) of 1-4 × 10-18 ergs s-1 cm-2 arcsec-2. The sensitivity of the search was calibrated using simulations with synthetic features added to the data frames. The data set upper limits on the mean space density 〈n〉 and line flux of randomly distributed Lyα-emitting clouds; for example, at z ≈ 4.5 we have a 95% confidence limit of 〈n〉 < 1 Mpc-3 h1003 at a total line flux level of ∼3 × 10-17 ergs s-1 cm-2. These limits approach expected emission levels for fairly conservative published primeval galaxy models. In addition, Lyα emission was searched for, but not detected, from a known Lyα-limit absorption cloud toward QSO 0731+653. Assuming that the gas in this cloud is spatially resolved (size ≳ 4h-1 kpc) we set an upper limit on the diffuse ionizing flux density at z = 2.912 of Jv ≲ 2 × 10-19 ergs s-1 cm-2 sr-1 Hz-1.
Specific-Heat Study Of The Anomalous Quantum Limit Of (Tmtsf)2clo4, Nathanael A. Fortune, J. S. Brooks, M. J. Graf, G. Montambaux, L. Y. Chiang, Jos A.A.J. Perenboom, D. Althof
Specific-Heat Study Of The Anomalous Quantum Limit Of (Tmtsf)2clo4, Nathanael A. Fortune, J. S. Brooks, M. J. Graf, G. Montambaux, L. Y. Chiang, Jos A.A.J. Perenboom, D. Althof
Physics: Faculty Publications
We report calorimetric measurements of the organic conductor (TMTSF)2ClO4 in the quantum limit. In addition to the field-induced spin-density-wave (FISDW) phases, we have measured the magnetic-field-dependent specific heat associated with the recently discovered reentrant phase. In terms of a semiempirical model, we find that the reentrant transition is second order, but that the electronic density of states is greatly reduced in the reentrant phase. We also observe a specific-heat signal corresponding to the anomalous fast oscillations which are known to coexist with the FISDW phases.