Disintegration Scheme of Long-Lived Aluminum-26

Abstract

The disintegration scheme of the long-lived ground-state isomer of Al 26 has been determined. It is based on the following observations.The maximum positron energy as determined by absorption measurements is 1.16±0.05 Mev; this agrees with the expected 1.17 Mev. The spectrum appears to be simple.The scintillation gamma spectrum shows intense positron annihilation radiation, a strong peak at 1.83 ±0.03 Mev, and weak peaks at 1.12=k0.03 Mev and 2.96±0.05 Mev, corresponding to transitions from the known Mg 26 states at 1.82 and 2.97 Mev. A peak at 0.68 Mev is from the addition of two annihilation photons, one being backscattered from the source and surroundings; the gamma of ^0.7-Mev energy reported by others is not present. The peak at 2.97 Mev is shown to result from 2.97-Mev photons as well as from addition of 1.82-and 1.15-Mev photons.The relative intensities of the annihilation and gamma radiations indicate that Al 26 undergoes (84.6 ±1.8)% positron emission to the 1.82-Mev state of Mg 26 ; (11.4±1.9)% electron capture to the same state; (3.7±0.3)% electron capture to the 2.97-Mev state followed by emission of 1.15-and 1.82-Mev gamma-rays; and (0.30±0.03)% electron capture to the same state followed by 2.97-Mev radiation. Other energetically possible transitions are apparently negligible in intensity.Auger electrons and x-rays were observed in a proportional counter spectrometer. Analysis of the spectra yielded iC-shell fluorescence yields of 0.008±0.003 for magnesium and 0.008±0.003 for aluminum.

Triggered Star Formation inside the Shell of a Wolf–Rayet Bubble as the Origin of the Solar System

“…Since 26 Al is not produced in the W-R stage but is mixed in with the shell during this stage, we allow for the decay of the 26 Al in the W-R phase, which lasts for a maximum period of t d = 300,000 yr (we do not consider smaller W-R periods because given the half-life of ~0.7 Myr, a smaller W-R phase will not lead to significant decay and thus further bolsters our arguments). We use a halflife of 26 Al of 7.16 × 10 5 yr (Rightmire et al 1959;Samworth et al 1972). After 26 Al is all mixed in, we assume that some fraction of the shell collapses to form a dense molecular core that will give rise to the proto-solar nebula.…”

Triggered Star Formation inside the Shell of a Wolf-Rayet Bubble as the Origin of the Solar System

“…Since 26 Al is not produced in the W-R stage, but is mixed in with the shell during this stage, we allow for the decay of the 26 Al in the W-R phase, which lasts for a maximum period t d = 300,000 years (we do not consider smaller W-R periods because given the half-life of ∼0.7 Myr, a smaller W-R phase will not lead to significant decay and thus further bolster our arguments). We use a half-life of 26 Al of 7.16 ×10 5 years (Rightmire et al 1959;Samworth et al 1972). After 26 Al is all mixed in, we assume that some fraction of the shell collapses to form a dense molecular core that will give rise to the proto-solar nebula.…”

Nuclear chemistry and geochemistry research. Carnegie Institute of Technology and Carnegie--Mellon University. Summary report

“…L. Leroy Lewis: 1950 Robert W. McKelvey: 1950 Donald G. Schindler: 1951 R. Joseph Ransil: 1951 John W. Cooper: 1951 Virginia A. Schultz: 1952-1955 James I. Nixon: 1953-1955 Gaile R. Ventresca: 1956 Philip M. Tischler: 1956 Glenn I. Henrickson: 1956 Michael J. Toia: 1957-1959 Thomas A. Becker: 1957-1959 Jane S. Potter: 1958-1961 Edward A. Ondovchik: 1959 Mark I. Appelbaum: 1961 Martha R. Miller: 1962 Michael L. Bender: 1964 Sanford J. Catz: 1964 Frederick J. Van Itallie: 1965 Richard G. Sextro: 1965-1966 Harold J. Konish: 1969 Mark J. Yeager: 1969-1971 Nina A. Landes: 1969 James D. Ulmer: 1970 John A. Yokum, Jr.: 1970 John F. Monahan: 1970 Charles A. Ritter: 1970 Peter Kamarchik: 1971 Stanley B. Nachimson: 1972-1973 Robert A. Witter: 1973-1974 Daniel L. Menis: 1973-1974 D. Lynn Svec: 1973-1974…”