Triton Beta Decay Research Articles

Half-life and [formula omitted] value for the bare triton

Experimental and theoretical data on the atomic effects accompanying triton beta decay have been used to derive the bare triton half-life both for the case where only electrons of the continuous spectrum are formed and for the case where decay to bound states in the 3He+ ion is taken into account, and to calculate the comparative half-life which proved to be fT1/2=1129.6±3.0 s. Estimate of the ratio of axial-vector-to-vector weak coupling constants for the triton beta decay (GA/GV)t=−1.2646±0.0035 has been obtained from the relation connecting GA/GV and fT1/2.

Difference between the triton beta decay constants in atomic and molecular tritium measured by the helium isotope method

The results are given for an experiment on measuring the difference between the values of triton beta decay constant in atomic and molecular tritium, Δλam=λa−λm. In order to determine Δλam, the growth rates of the relative content of radiogenic helium-3 in samples with atomic and molecular tritium have been compared. The value of Δλam=(4.6±0.8)×10−12 s−1 has been obtained, which corresponds to a relative change of the decay constant by ∼0.26%. Using the value of Δλam measured, the following value of the half-life of atomic tritium has been derived: (T1/2)a=(12.264±0.018) years.

Determination of the ratio of the axial-vector to the vector coupling constant for weak interaction in triton beta decay

Data on the chemical shifts of the half-lives of atomic and molecular tritium are used to determine the ratio of the axial-vector to the vector coupling constant for weak interaction in triton beta decay. The result is (GA/GV)t=−1.2646±0.0035.

Rho-meson exchange three-body force effects.

For each of several proposed \ensuremath{\pi}-meson cutoff masses (${\mathrm{\ensuremath{\Lambda}}}_{\mathrm{\ensuremath{\pi}}}$) in the \ensuremath{\pi}NN form factor, we obtained \ensuremath{\rho}-meson cutoff mass (${\mathrm{\ensuremath{\Lambda}}}_{\mathrm{\ensuremath{\rho}}}$) in the \ensuremath{\rho}NN form factor so that the three-body force with these form factors may reproduce the triton binding energy. We calculated the wave function and the exchange current in the Gamow-Teller matrix element for the triton beta decay, consistently using these form factors. The most favorable set ${\mathrm{\ensuremath{\Lambda}}}_{\mathrm{\ensuremath{\pi}}}$=0.81 GeV and ${\mathrm{\ensuremath{\Lambda}}}_{\mathrm{\ensuremath{\rho}}}$=1.13 GeV yielded a triton binding energy of 8.485 MeV (experimentally, 8.482 MeV) and a Gamow-Teller matrix element divided by \ensuremath{\surd}3 0f 0.955 (experimentally, 0.961).

The triton beta decay, a test of the axial vector

The expectation value of the axial-vector matrix element is calculated in the beta decay of the triton. Using a realistic wave function and including effects from pion and rho-meson exchange, as well as relativistic corrections to the one-body operator, we obtain agreement with the experimental value deduced 〈 στ〉=√3 (0.958 ± 0.008) .

Vector-meson exchange currents in the triton beta decay

Vector-meson exchange currents in the triton beta decay

Calculation of meson-exchange corrections to triton beta decay using realistic nuclear wave functions

Abstract The one-pion-exchange contribution to the axial-vector matrix element for 3 H → 3 He + e − + g n e is calculated. The model of Cheng, based on CVC and PCAC, is used to determine the corrections to the axial-vector operator, and trinucleon wave functions are calculated by solving the Faddeev equations for the Reid soft-core nucleon-nucleon potential. The S-D transition matrix elements give the dominant contributions in agreement with previous results of Blomqvist and of Riska and Brown.

Tensor force and exchange currents in the triton beta decay

We estimate the correction due to exchange currents to the one-body 3 H → 3 He β-decay amplitude, treating the D-state part of the wavefunction in a simple approximate way. We find the main effect to come from the S-D cross terms.

Low-energy theorem for exchange axial-vector currents

A low-energy theorem is given for the two-body exchange current of axial-vector type. The exchange current is divided into two parts, the one directly related to the nuclear forces and the remainder, and the numerical results for the former are shown to be in good agreement with experiments for the beta decay of triton.

PCAC and triton beta decay

The PCAC relation is used to derive the one-pion-exchange contribution to the allowed Gamow-Teller beta-decay operator. The transition matrix element is evaluated for the 3 H → 3 He decay. The resulting correction is found to account for the difference between the experimental and the one-body matrix elements. The S-D cross terms give the main contribution.

PCAC and interaction current effect in triton beta decay

We use the low-energy theorem for the axial current to obtain the part of the interaction current contribution to nuclear beta-decay coming from the ‘non-Born terms’. In triton beta-decay this turns out to be quite substantial, but is cancelled mostly by the part of the ‘Born term’ not included in the nuclear wave function. The effect of a repulsive core is also examined.