Endpoint energies (Qp-values)

Accurate measurements of Qp aid considerably the determination of the energies of individual P- emissions, and in the derivation of the mean beta energies (and gamma energies) of short-lived fission products. Rapid mass-separation techniques are used to alter the isobaric composition of the ion beams after their emission from fission targets, and high-purity Ge detectors measure the P-у coincidence and P singles spectra of the resulting sample (Wtinsch et al, 1978; Przewloka et al, 1992a and 1992b; Ikuta et al, 1994).

The beta endpoints are determined from Fermi-Kurie plots of the measured P — spectrum (Fermi-Kurie plot with good statistics is shown in Fig. 30 for 92Rb (Przewloka et al, 1992a)). Equivalent data for a number of neutron-rich nuclides are listed in Table 13 (Ikuta et al, 1994), and are compared with the recommended values of Audi and Wapstra (1995). Discrepancies do occur (147La, 147,149,150Ce and 150Pr), and underline the need to refine theoretical calculations in this particular region.

1.5 —

1.0

0.5 0.0

7414

Table 13: Qp values of neutron-rich nuclei in the mass region 147<A<152 (Ikuta et al, 1994)

Nuclide

Half-life

Measured Qp (keV)

Qp (keV)

Audi and Wapstra, 1995

147La

4.015 s

5130(80)

4945(55)

147Ce

56.4 s

3426(28)

3290(40)

147Pr

13.3 m

2710(50)

2686(37)

148Ce

56 s

2140(30)

2060(75)

148Pr

2.27 m

4880(50)

4932(89)

149Ce

5.2 s

4386(27)

4190(75)

149Pr

2.26 m

3430(90)

3397(10)

150Ce

4.0 s

3470(60)

3010(90)

150Pr

6.19 s

5390(30)

5690(80)

151Pr

18.90 s

4200(40)

4101(35)

151Nd

12.44 m

2460(100)

2442(4)

152Pr

3.24 s

6340(120)

6444(300)

152Nd

11.6 m

1100(40)

1110(78)

152Pm

4.1 m

3520(60)

3504(72)

Uncertainties are given in parentheses (for example, 4945(55) means 4945 ± 55).

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