1,588 Matching Results

Search Results

Advanced search parameters have been applied.

Global Infrasonic Monitoring of Large Bolides.

Description: Using recent infrasonic data (1995-2001) and older infrasonic data recorded by AFTAC (1960-1974), we have refined our estimates of the global influx rate (cumulative influx) of large bolides with sufficient strength to deeply penetrate the atmosphere (below {approx} 50 km). The number of bolides arriving as a function of their initial source energy has been estimated from a least-squares curve-fit of our database of 19 bolides (for a source energy > 0.053 kt) with the resulting values and an estimate of the associated statistical counting errors: 30.3{+-} 6 bolides at {ge}0.1 kt, 5.8{+-} 2 at {ge}1 kt and 0.84{+-} 0.25 at {ge}15 kt. In this work we also used these estimates to infer the recurrence interval for energy levels slightly outside the original source energy range, The Tunguska bolide of 1908 ({approx}10 Mt) is a prime example of a previously observed body of great interest. Almost regardless of how we analyze the recent data, the conclusion is that bolides with Tunguska type energy levels should reoccur on the average every 120{+-}10 years.
Date: January 1, 2001
Creator: ReVelle, D. O. (Douglas O.)
Partner: UNT Libraries Government Documents Department

Results from GAMMASPHERE in the A {approx} 80 mass region

Description: We present recent results obtained with GAMMASPHERE for nuclei in the A{approx}80 mass region. These studies have concentrated on a systematic study of superdeformed bands and their transitional quadrupole moments. Normally-deformed rotational bands in a series of even-even T{sub z} = 1 nuclei were also investigated to probe the possible influence of the np pairing on the structure of their yrast bands.
Date: August 2, 1996
Creator: Rudolph, D.; Baktash, C. & Brinkman, M.J.
Partner: UNT Libraries Government Documents Department

Radiochemical investigations of nuclear properties. Progress report, 1 October 1974--30 September 1975

Description: Further studies of the structure of nuclei in the A = 180-200 shape transitional region have been performed. The principal project completed during the current year was an extensive in-beam $gamma$-ray investigation of high-spin levels in the nine nuclei $sup 186$Pt to $sup 194$Pt by ($alpha$,xn$gamma$) reactions on enriched Os targets. Acute backbending observed in the positive parity yrast sequences of $sup 188$,$sup 190$,$sup 192$,$sup 194$Pt has been attributed to the intersection of rotation-aligned ($nu$i-$sup 2$/sub 13/2/) and ($pi$h$sup -2$/sub 11/2/) bands with the ground bands. In all four odd-A Pt nuclei, decoupled $nu$i$sup -1$/sub 13/2/ bands and many other low-lying high- spin positive parity levels have been established, and low-spin positive parity levels have been located in complementary decay studies. A model of an i/sub 13/ 2/ neutron hole coupled to a triaxially deformed core has been found to be rather successful in reproducing these complex level spectra. Other topics dealt with include new $mu$s isomers in $sup 187$,$sup 189$,$sup 191$Pt, the decays of $sup 191$Au, /sup 194m/Ir and 1.7 h $sup 186$Ir and the level structure of $sup 191$Au from an $sup 191$Ir(alpha,4n$gamma$) study. (auth)
Date: September 1, 1975
Creator: Daly, P.J.
Partner: UNT Libraries Government Documents Department

Effective three-body forces in truncated shell-model calculations

Description: From Symposium on correlations in nuclei; Balatonfured, Hungary 13 8ep 1973). The problem of the determination of effective Hamiltonians to be used in shell model calculations in a truncated vector space is studied in more detail by undertaking a series of calculations in which one can make a direct connection between a fixed Hamiltonian H, which describes the eigenenergies and eigenvectors of nuclei in a given mass range in some large shellmodel vector space S, and an effective Hamiltonian H/sup 1/ to be used to describe some of the eigenvalues and eigenvectors of the same nuclei in a smaller (truncated) vector space S/sup 1/. These methods are applied to oxygen 19, fluorine 19, and neon 20. (JFP)
Date: January 1, 1973
Creator: Barrett, B.R.; Halbert, E.C. & McGrory, J.B.
Partner: UNT Libraries Government Documents Department

Distributions, fluctuations, and symmetries in many-particle spectroscopy

Description: The state density for a spectroscopic system of many interacting particles is determined to a large extent by the operation of a central limit theorem which fixes the averaged form, while, throughout the entire spectrum, the fluctuations about the average closely follow the laws, derived for high excitation energy, by considering random matrix ensembles. The fluctuations are small, the Dyso Mehta description of the random ensemble spectra as essentia, crystalline'' being found to apply much more generally. The same general results obtain, both for averages and fluctuations, under a restriction to states of given exact symmetry, and, for the averages, even for broken symmetries. Other properties of the system, occupancies for example, are determined similarly. (auth)
Date: September 1, 1973
Creator: French, J.B.
Partner: UNT Libraries Government Documents Department

Some perspectives on high-spin physics. [Concluding talk]

Description: This report consists of a talk presented at the conclusion of a meeting. As is typical, this talk does not truly summarize what was said at the meeting; the author acknowledges that he discusses several areas of interest to him - some of which were covered at the meeting and some of which were not. High-spin phenomena are divided into collective and noncollective regions, each of which exhibits resolved and unresolved ..gamma.. rays. Rotational spectra in the unresolved collective region are discussed; correlations between ..gamma..-ray energy and spin and between ..gamma..-ray energies in a rotational nucleus are pointed out. In the resolved noncollective region, the spectrum of /sup 152/Dy exhibits a straight line when energy is plotted vs I(I+1); it is concluded that shell effects explain this behavior. In summary, the author in his talk has tried to indicate areas of current research interest. 10 figures. (RWR)
Date: August 1, 1979
Creator: Stephens, F.S.
Partner: UNT Libraries Government Documents Department


Description: Tables of gamma-ray transition probabilities predicted by the asymmetric rotor model of even-even nuclei were calculated. Tables are also presented on the coefficients of the rotational wave functions as a function of k, the asymmetry parameter. A third table gives the values of parameters needed to calculate energy levels in the hydrodynamical model using molecular spectroscopy tables. (C.J.G.)
Date: August 1, 1960
Creator: Day, P.P. & Mallmann, C.A.
Partner: UNT Libraries Government Documents Department