Hot-atom chemistry

Research in the chemical effects of the nuclear transformations during the past 50 years is reviewed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43111/1/10967_2005_Article_BF02039469.pd

Energetic Recoil Atom Reaction Mechanisms: Progress Report No. 2

US AEC Contract No. AT(11-1)-912. UM report 3710-2-Phttp://deepblue.lib.umich.edu/bitstream/2027.42/86067/1/MMPP 167-3 Feb 1962.PDF-

Energetic Recoil Atom Reaction Mechanisms: Progress Report No. 1

US AEC Contract No. AT(11-1)-912, UM report ORA 3710-1-9.http://deepblue.lib.umich.edu/bitstream/2027.42/85777/1/MMPP 167-1 March 1961.PDF15

Reactions of High‐Energy, Excited I128 Ions with Gaseous Molecules

The manner in which molecular additives inhibit the reaction of (n, γ) activated I128 with CH4 was determined in an effort to observe indirectly reactions of I128 with the additives. The data suggest that (1) O2, N2, and CF4 serve only to remove excess I128 kinetic energy; (2) the ionization potential of O2 is greater than 12.16 ev, the potential energy of I+(1D2); (3) the ionization potential of C2F6 is less than 12.16 ev; (4) CH3I, CF3I, n‐C3H7I, and C6H6 inhibit the reaction principally as a result of I++additive ion‐molecule reactions and/or physical quenching.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70530/2/JCPSA6-36-2-287-1.pd

Interpretation of Hot‐Atom Data

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71353/2/JCPSA6-39-10-2770-1.pd

C13 and Deuterium Isotope Effects in the Photolysis of Methyl and Ethyl Bromide

Relative rates of formation of isotopic radicals in the photolysis of gaseous methyl and ethyl bromide have been measured. Photolyses (2537 A) were carried out in a large excess of cyclopentane. Methyl (or ethyl) radicals formed in the primary C☒Br bond scission abstract H from cyclopentane to form methane (or ethane). For methyl bromide, the C12/C13 enrichment factor for the first fraction of the methane was 1.039±0.003. The corresponding factor for the α‐carbon—Br rupture in ethyl bromide was 1.041±0.004. In the deuterium experiments, CH3Br—CD3Br mixtures in excess cyclopentane were photolyzed. The H/D fractionation factor (based on CH4/CD3H) was 1.41±0.01.The difference in rates of formation of isotopic radicals is due to the difference in ultraviolet absorption coefficients of the isotopic alkyl bromides. At 2537 A the observed ratio of the extinction coefficient of CH3Br relative to that of CD3Br is 1.38±0.05.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71079/2/JCPSA6-30-4-973-1.pd

Failure to Bond Rupture and Nuclear Recoil Following (n, γ) Activation

Following the absorption of a thermal neutron by 127I or 79Br, the neutron‐binding energy is frequently released in the form of a gamma‐ray cascade. As a result of partial cancellation of gamma‐ray momenta, a small fraction of the activated halogens will not receive sufficient recoil momentum to rupture from their parent compound. The gas‐phase failures to bond rupture following 127I(n, γ) 128I, and 79Br(n, γ) 80Br activation were found experimentally to be: CH3I—1.09, CD3I—0.68, CF3I—0.12, CH2I2—0.068, C2H5I—0.082, n‐C3H7I—0.66, i‐C3H7I—0.30, CH3Br—0.25, CD3Br—0.20, CH2Br2—0.12, CF3Br—0.11, CF2Br2—0.093, CHClBr2—0.087, CCl3Br—0.066, CHBr3—0.05, CBr4—0.03, C2H5Br—0.33, and 1,1‐C2H4Br2—0.17%. These data are correlated with the calculated recoil energies required for bond rupture (preceding article). Using as a basis the distribution of net gamma‐ray energies calculated by the random‐walk method for the 35Cl(n, γ) 36Cl process, the kinetic‐energy distributions of the dissociated 128I or 80Br are approximated. These data suggest that the extent of hot‐atom reaction of 128I or 80Br with CH4 should not depend upon the parent molecule from which the activated halogen dissociates.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69788/2/JCPSA6-36-4-954-1.pd

Obsidian Samples from Archaeological Sites in Northwestern Alaska: A Preliminary Report

Reports the Na and Mn contents and Na/Mn ratios, determined by neutron activation analyses of 103 obsidian samples from the Onion Portage and nine related archeological sites. The occurrence and stratigraphic distribution are noted of four groups of obsidian distinguished by Mn content and Na/Mn ratio. Group B, the largest, appears in a complex with an age of 4000-3900 BC and in another of 1000-1700 AD, group A in complexes dating at 2600-2200 and 1500-500 BC, group C occurs 2200-1800 BC; and group D 400-1700 AD. There are at least four obsidian sources represented whose geographic locations are unknown

A Closed General Solution of the Probability Distribution Function for Three‐Dimensional Random Walk Processes

A closed general solution of the probability distribution function for three‐dimensional random walk processes is derived. In addition: (1) For the particular case of equal‐length displacements, the exact solution is compared with the Gaussian approximation for n=3, 5, and 10 steps. (2) The general solution is utilized in calculating the probability distribution of gamma‐ray energies resulting in the Cl35 (n, γ) Cl36 process. (3) For five unequal steps of fractional length: 0.582, 0.135, 0.131, 0.092, and 0.060 (which is somewhat characteristic of the fractional energies of gamma rays resulting from neutron capture), the exact solution is compared with a Gaussian, a modified Gaussian, and a five equal‐step approximation. (4) There are presented the specific solutions for all possible unequal‐length random displacements involving n=2, 3, and 4 steps.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70032/2/JCPSA6-34-2-535-1.pd

Energy‐Distribution Function for Hot Atoms Produced by Nuclear Transformations

The energy‐distribution function for hot atoms produced by nuclear transformations is examined in terms of the fraction of the initial hot‐atom energy. Energy dependent and independent asymmetric scattering is specifically considered. For gaseous tritium generated by the 3He(n, p) process, the asymptotic solution probably can serve as a reasonable approximation of the distribution function in the energy range 2–20 eV. For hot atoms produced with an initial distribution of energies, such as 79Br(n, γ)‐produced 80Br, the asymptotic solution will be less valid than for tritium, but may still be a valid approximation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70454/2/JCPSA6-41-6-1595-1.pd