Fermi-Kurie Plot Research Articles

Evidence of sterile neutrino from endpoint analysis of β-spectrum

An anomaly has been observed around the endpoint of the measured β spectrum of second unique forbidden transition of 138La(5+). The data has been analyzed in the light of Fermi–Kurie plot and an extra component around the endpoint energy has been observed at a 3σ level of statistical significance. The probability of observing that extra component with respect to the beta events are same (⩽0.01%) in a number of repeated experiments and the fitted parameters of the extra strength with Gaussian shape around endpoint energy are within the error of 99.7% confidence limit. All possible tentative explanation in the light of atomic, nuclear and neutrino physics have been discussed. A favorable tentative explanation could be existence of the sterile neutrino. The present data analysis provides mass limit, 15 ± 9 ± 4 (sys.) ⩽ m 4 (keV) ⩽ 45 ± 27 ± 4 (sys.) for active-sterile mixing ratio 0.3 ⩾ |U e4|2 ⩾ 0.03.

Practical Qβ analysis method based on the Fermi–Kurie plot for spectra measured with total absorption BGO detector

A practical method based on Fermi–Kurie plots was newly proposed in order to analyze β-decay energy ( Q β) measured with a total absorption BGO detector. The detector has large efficiencies; all β-rays and subsequent γ-rays can be absorbed simultaneously, and the endpoint energy of the spectrum shows the Q β. In the spectrum, different β-rays having maximum endpoint energies and forbiddenness are superimposed. To apply this method to the measured spectra, in addition to a simplified decay scheme that has a one-component β-ray fed to a pseudo-level E γ, a mixed transition of the allowed and the unique-type first-forbidden transitions with a ratio of α was newly taken into account. Using the theoretical β-ray spectra, we verified that the Q β can be deduced without information about the decay scheme, and described the dependences of the derived Q β on E γ and α. We also checked the reliability of this method by analyzing the spectra of fission products of 91 − 94Rb, 139 − 143Cs, 142Ba and 142,144La, which had well-determined Q β up to 11 MeV. Consequently, we proposed that this method was applicable for analyzing spectra with a systematic uncertainty of 60 keV, when the analyzing regions were limited to about 1 MeV below the Q β. Then, this method was also applied for re-analysis of the Q β of neutron-rich rare earth nuclei.

Computer simulation of positron-induced radiation effects in Dynamic RAMs

The sensitivity of computer memory devices to single event upsets (SEUs) caused by ionizing radiation provided the foundation for a proposed dynamic Random Access Memory (DRAM) based position sensitive radiation sensor, which is likely to be used for studying the movement of radiolabelled pharmaceuticals in biological tissues in vitro using positron emitting tracers. By making use of the ITS [8] Monte Carlo code, simulations of the positron interactions with the materials consisting a DRAM device have been carried out for four positron emitters, i.e. 18F, 13N, 11C and 15O, which are of interest in studying biological functions. The device geometry modelling and the positron energy spectra of the above emitters obtained by utilizing the Fermi-Kurie plots have been successfully applied. Finally, the energy deposition of positrons within the different layers of the DRAMs were investigated. The aim of this paper is to present and discuss the results of these simulations.

A 4π CaF2(Eu) scintillation spectrometer for measurements with X-ray and electron sources

A 4π CaF2(Eu) scintillation spectrometer is described which is suitable for measurements with electrons and X-rays. The detection efficiency for these radiations has been measured using 32P and 109Cd sources respectively. In addition, the resolution, linearity of response and total photon efficiency have been determined for this detector as functions of incident radiation energy. An insensitive region on the surfaces of CaF2(Eu) crystals was determined to be (0.47 ± 0.10) mg/cm2 thick using a collimated 252Cf α-source. A brief study of negaton and positon continuum spectra, obtained using 32P and 120Sb sources respectively, is also described together with the corresponding Fermi-Kurie plots.

A Sector-Type Beta-Ray Spectrometer: A Laboratory Experiment

A simple inexpensive sector-type beta-ray spectrometer which can be constructed using any available electromagnet with flat circular pole pieces is described. Such a spectrometer can be used to demonstrate the continuous nature of the beta spectrum and the existence of internal conversion lines, and also to determine the end-point energy of a beta spectrum by drawing the Fermi-Kurie plot.

New isotopes 73Zn and 74Zn

The decay characteristics of the new neutron-rich isotopes 73Zn and 74Zn have been investigated using isotopically separated samples produced by the ISOLDE on-line facility. Beta and γ-ray spectra were recorded, partly in coincidence, by means of a Ge(Li) and a plastic detector. Beta end-point energies have been determined from the Fermi-Kurie plot as well as from a cube-root plot. The Q-values of 73Ga and 74Ga were remeasured to 1.61 ± 0.10 MeV and 5.3 ± 0.2 MeV. The following half-lives and Q-values were assigned to the new Zn isotopes: 73 Zn: T 1 2 = 23.5 ± 1.0 sec, Q β≧4.7 MeV, 74 Zn: T 1 2 = 98 ± 2 sec, Q β≧ 2.1 MeV .

Decay of 121mSn and 121Sn

The decay schemes of 121Sn and 121Sn have been investigated with a 4 π beta spectrometer and β-γ coincidence techniques. The beta spectrum of 121mSn has an end-point energy of 354 ± 5 keV and yields a linear Fermi-Kurie plot when a first-forbidden unique shape factor is applied. The 121Sn half-life was found to be 25.5 ± 0.1 h, and the beta speectrum had an end-point energy of 383 ± 3 keV. From the beta spectra and the 121Sb level structure, the 121Sn level was found to be 8 ± 5 keV above the 121Sn ground state. The spin and parity assignments for the 121Sn and 121Sn states are in agreement with the shell model. The 37 keV 121Sb transition which follows the decay of 121Sn was investigated by using a Li-drifted silicon detector. A γ-ray energy of 37.15 −0.02 +0.04 keV and a K internal-conversion coefficient of α K = 9.32±0.37 were obtained.

ELECTRON SPECTRA IN THE DECAY OF THALLIUM-204

The continuous beta spectrum and the K Auger-line spectrum in the decay of 204Tl were investigated using a high-resolution, iron-free, [Formula: see text] double-focusing spectrometer. Instrumental distortion of the beta spectrum was shown to be very small and a linear Fermi–Kurie plot was obtained using the generalized unique first forbidden shape factor bq2 + λ2p2, with b = 1.161 ± 0.005. The end-point energy was determined to be (763.24 ± 0.31) keV. Measured values for the energies and relative intensities of the K Auger lines were in broad agreement both with theory and with previous experimental work. The K fluorescence yield was estimated to be 0.97 ± 0.017.

Decay ofNb94andNb94m

The beta decay of 2.0\ifmmode\times\else\texttimes\fi{}${10}^{4}$-yr ${\mathrm{Nb}}^{94}$ has been investigated by means of a scintillation spectrometer. The beta spectrum has an end-point energy of 470\ifmmode\pm\else\textpm\fi{}6 keV and yields a linear Fermi-Kurie plot when a shape factor of ${p}^{2}+\ensuremath{\lambda}{q}^{2}$ $\ensuremath{\lambda}=1.75\ifmmode\pm\else\textpm\fi{}0.15$ is applied. The shape factor indicates the transition is second-forbidden non-unique, in accord with its $log\mathrm{ft}$ value of 12. Additional measurements were made of electromagnetic radiations from both ${\mathrm{Nb}}^{94}$ decay and that of 6.6-min ${\mathrm{Nb}}^{94m}$ No new transitions were observed, but more precise energy determinations of the gamma rays emitted in the decay of ${\mathrm{Nb}}^{94}$ were obtained. The results of this study further support previously proposed spin and parity assignments.

Beta-spectrum shape measurements with a 4π semiconductor spectrometer

A 4π semiconductor spectrometer employing diffused window lithium-drifted silicon detectors has been constructed. It was tested by varying the parameters of the system, so as to eliminate possible sources of distortion. It was further tested by measuring the shapes of two simple β-spectra ( 143Pr and 185W) and two inner group β-spectra ( 198Au and 86Rb) in coincidence with the subsequently emitted γ-rays. The γ-ray pulse, detected by a NaI well counter that envelops the beta spectrometer, supplied the gate to the 400-channel pulse-height analyser. In all cases, the results of these measurements are in good agreement with those previously reported. The beta spectrum of the 170Tm decay to the first excited level in 170Yb was measured in coincidence with the 84 keV gamma ray. The experiment was performed under the same measurement conditions used for the 198Au and 86Rb experiments. The spectrum exhibits a definite non-statistical energy dependence, falling below any straight line Fermi-Kurie plot fit at low energies. The shape factor was fitted by a polynomial of the form 1+ aW+ b/ W+ cW 2. A good fit was obtained for a = 1.11, b = −0.85, c = − 0.24. The end-point of this transition was determined to be 879±7 keV.

A study of 123Sb levels populated in the beta decay of the high spin isomer of 123Sn

Several nuclear energy levels in 123Sb populated by the β − decay of 125 d 123Sn have been examined. The presence of two states at 1032 and 1089 keV was deduced from studies utilizing a Ge(Li) gamma-ray spectrometer and a third state, at 1187 keV, has been proposed on the basis of gamma-ray coincidence measurements. The β − spectrum to the 1089 keV state was studied by means of a 4 π plastic scintillator operating in coincidence with a NaI(Tl) gamma-ray spectrometer. A Fermi-Kurie plot of the spectrum was found to be linear indicating that the transition is either allowed or non-unique first forbidden. The log ft value of 9.0 found for this transition tends to support the latter assignment.

Fermi-function integrals for finding relative beta-group intensities

Values are presented of the definite integral I ( Z, T max ), which is related to the relative number, N , of electrons in a β − -group with end point energy T max by the simple expression N = a 2 T max 2 I ( Z , T max ), where a is the y -intercept in the Fermi-Kurie plot, I ( Z , T max ) = ∫ 0 T max f ( Z , T ) h ( T ) d T , where f is the Fermi function and h ( T ) = ( T + 1 ) ( 1 − T / T max ) 2 [ T ( T + 2 ) ] − 1 / 2 T max − 2 . The Z -ranges is 10(1)109; the T max -range is 0.1(0.05)0.4, 0.5(0.1)5.2.

Positron Decay ofCo58

The allowed positron transition from the Co/sup 58/ ground state (2+) to the Fe/sup 56/ first excited state (2+, 810 kev) was studied using a 4 pi positron-scintillation spectrometer. The experimental shape factor exhibits a small systematic deviation from that theoretically predicted for an allowed transition and corresponds to an excess of low-energy positrons. The experimental shape factor can be fit by a curve proportional to (1 + b/W) with b = 0.3. The FermiKurie plot is linearized by this correction factor and yields an end-point energy of 474 plus or minus 5 kev. Similar discrepancies between the experimental and theoretically predicted shapes of Gamow-Te-ller beta transitions for negatrons (In/sup 114/, P/sup 32/, and Y/sup 90/) and positrons (Na/sup 22/) have been reported. In these cases it was found that this same shape factor with 0.2 < b < 0.4 would linearize the theoretically-corrected Fermi-Kurie plots. No satisfactory explanation for this effect has been offered. As previously suggested by other investigators, the shape factor (1 + b/W) must, for the present, be regarded as a purely empirical correction. The end-point energy from the present investigation combined with the recent high-precision measurement of the gamma-ray transition energy from the first excitedmore » state to the ground state of Fe/sup 58/ yields a Co/sup 58/-Fe/sup 58/ mass difference of 2306 plus or minus 5 kev. (auth)« less

Beta Decay of Naturally RadioactiveIn115

A liquid scintillator loaded with indium has been used to study the fourth-forbidden beta decay of ${\mathrm{In}}^{115}$. Specific activity measurements yield a half-life of (6.9\ifmmode\pm\else\textpm\fi{}1.5)\ifmmode\times\else\texttimes\fi{}${10}^{14}$ years. A crude beta spectrum was obtained. Linear extrapolation of the Fermi-Kurie plot gives an end-point energy of 625\ifmmode\pm\else\textpm\fi{}70 kev.

Small Deviations Observed in Beta Spectra:In114,Y90, andP32

The beta spectra of ${\mathrm{In}}^{114}$, ${\mathrm{Y}}^{90}$, and ${\mathrm{P}}^{32}$ (all of which decay by pure Gamow-Teller radiations) have been very carefully studied in a magnetic spectrometer. The Fermi-Kurie plots of all three spectra exhibit small deviations from linearity corresponding to an excess of low-energy electrons. All of the evidence indicates that the observed nonstatistical shapes represent the true spectra and are not the result of instrumental distortions. The Fermi-Kurie plots of these three isotopes can be linearized by a ($1+\frac{b}{W}$) correction factor (in addition to the once-forbidden, unique shape factor in the case of ${\mathrm{Y}}^{90}$).

Small Deviations Observed in Beta Spectra:Na22

The intense positron spectrum of ${\mathrm{Na}}^{22}$ has been carefully measured in a magnetic spectrometer. This transition proceeds from a 3+ to a 2+ level. The observed ${\mathrm{Na}}^{22}$ spectrum has a nonstatistical shape corresponding to an excess of low-energy electrons. The well-measured spectrum of ${\mathrm{Pm}}^{147}$ was reinvestigated and found to have a statistical shape. The many tests of the experimental procedures all indicate that the observed nonstatistical spectrum of ${\mathrm{Na}}^{22}$ is not the result of instrumental distortions. Theoretical refinements for finite de Broglie wavelength, screening, and possible contributions from the twice forbidden matrix elements were considered and found to be much too small to explain the deviation from the statistical shape observed in ${\mathrm{Na}}^{22}$. The Fermi-Kurie plot of ${\mathrm{Na}}^{22}$ can be linearized by a ($1+\frac{b}{W}$) correction factor. This same factor has been used to linearize the Fermi-Kurie plots of ${\mathrm{In}}^{114}$, ${\mathrm{Y}}^{90}$, and ${\mathrm{P}}^{32}$ (in addition to the once forbidden, unique shape factor in the case of ${\mathrm{Y}}^{90}$). In all four cases, the value of the parameter $b$ to yield a linear F-K plot is in the range $0.2lbl0.4$. At present, no theoretical explanation is offered for the correction ($1+\frac{b}{W}$). It may be regarded as an empirical correction capable of explaining the observed shapes in the case of these four Gamow-Teller transitions. A search was also made for negative electrons accompanying the normal positron decay of ${\mathrm{Na}}^{22}$. A weak, low-energy electron distribution was observed. This distribution may be explained by the theory of shake-off electrons.

Beta Decay ofC14and Nuclear Forces

The anomalously long lifetime of ${\mathrm{C}}^{14}$ is interpreted as being due to an accidental cancellation in the $\ensuremath{\beta}$-decay matrix element which is complete to about one part in 160. In the shell model with oscillator wave functions, general two-nucleon interactions are introduced which are linear in the velocities and which satisfy various invariance requirements. As many of the force parameters are determined from low-energy experimental nuclear data as possible. The strength of the spin-orbit force is fixed by the ${p}_{\frac{3}{2}}\ensuremath{-}{p}_{\frac{1}{2}}$ splitting in ${\mathrm{N}}^{15}$, while the tensor force is taken from meson theory. The conditions for cancellation are then shown to be satisfied, although uncertainties in the central force prevent an exact calculation of the wave functions. These uncertainties are therefore eliminated by requiring cancellation, in addition to fitting the three lowest energy levels of ${\mathrm{N}}^{14}$. The resulting ${\mathrm{N}}^{14}$ ground state wave function is mainly $D$-state, containing only 13% $P$- and 3% $S$-component, and checks satisfactorily against various experimental properties of ${\mathrm{N}}^{14}$. In addition, the $\ensuremath{\beta}$ decay of ${\mathrm{O}}^{14}$ is investigated and it is shown that the ${\mathrm{C}}^{14}$-${\mathrm{O}}^{14}$ difference in $\mathrm{ft}$-values is not adequately accounted for by the Coulomb repulsion theory of Jancovici and Talmi. The discrepancy is removed by including the slight difference in spin-orbit coupling strength for protons and neutrons, due to electromagnetic interaction with their magnetic moments. It is also pointed out that a nonlinearity of about 10% should be expected in the ${\mathrm{O}}^{14}$ Fermi-Kurie plot. In the appendices are a treatment of nucleon hole conjugation, an extension of a proof by Inglis on the impossibility of cancellation without the tensor force, a calculation of the $n\ensuremath{-}\ensuremath{\alpha}$ spin-orbit splitting, and an approximate treatment of the binding energy of the $\ensuremath{\alpha}$ particle.

The beta spectrum of carrier-free Ni 63

A method is given for the preparation of appreciable quantities of practically carrier-free Ni 63 from pile irradiations of copper via the Cu 63( n,p) reaction, which has an effective cross-section of 3 millibarns for the neutron spectrum encountered in a typical LITR irradiation. The beta spectrum was studied in a large gas proportional counter with carrier-free Ni 63 mounted on a saturation thickness of platinum foil placed as a platform inside the sensitive volume. The allowed Fermi-Kurie plot appears to be linear to 7·5 keV, which suggests that the decay probably belongs to the class of allowed transitions with exceptionally long half-lives, interpreted to be “ l-forbidden.” The endpoint of the beta-spectrum occurs at 67·0 ± 0·5 keV. The irradiation of spectroscopically-pure copper oxide powder produced appreciable amounts of Co 60 and Zn 65 corresponding to 0·6 p.p.m. cobalt and 1–2 p.p.m. zinc as subspectroscopic impurities in the target material.

Beta EmitterNp238. I. Beta Spectroscopy

The beta decay of ${\mathrm{Np}}^{238}$ has been studied with several beta spectrometers. In addition to the known conversion lines corresponding to transitions of energies now determined as 44.0, 102.2, 986, and 1029 kev, new conversion lines, corresponding to transitions of 942 and 927 kev were found. These transitions indicate the presence of closely spaced levels at higher excitation energies. Intensities of conversion lines and beta groups were determined and compared with previous work. Fermi-Kurie plots confirm the allowed shape of the hard beta group (1.25 Mev) and give indication of complexity in the soft beta group (0.27 Mev). The energy deviations of the ground rotational band levels from the simple rotational energy formula are discussed.

The beta-ray spectrum of 71arsenic

Synopsis The activity of 71 As, obtained by bombarding Ge with deuterons of 26 and 14 MeV has been investigated. From the decay of the electron line of 163,9 keV the half-life was found to be 59,5 ± 2 hours. The 175 keV γ -ray gave the ratio e K − /e L+M − = 8.3. The Fermi-Kurie plot of the positon spectrum allowed two interpretations: a simplex spectrum with endpoint at 800 keV or a complex one with end points at 675 and 850 keV. The two corresponding decay schemes are discussed. Four new electron lines were detected, which were ascribed to L - and M -conversion lines of a 13 keV γ -ray from 73 As, and to K - L , L and K - L , M Augerlines.