TABLE 1

Decay Data for the Electron Emitters Studied (22,23)

Element	Radionuclide	Decay mode	Half-life	p/e	Mean β-energy (keV/decay)	Mean electron energy (keV/decay)
Lanthanum	¹⁴⁰La	β⁻	1.68 d	4.3	525	9
	¹⁴²La	β⁻	1.54 h	3.0	842	—
Praseodymium	¹⁴²Pr	β⁻, EC	19.2 h	0.1	809	—
	¹⁴³Pr	β⁻	13.6 d	9.9 × 10⁻⁸	315	—
	¹⁴⁵Pr	β⁻	5.98 h	0.02	677	0.4
Promethium	¹⁴⁹Pm	β⁻	2.21 d	0.03	366	0.7
	¹⁵⁰Pm	β⁻	2.68 h	1.9	781	11
Samarium	¹⁵³Sm	β⁻	1.95 d	0.2	225	45
Europium	¹⁵⁰Eu	β⁻, β⁺, EC	12.6 h	0.1	299/(e⁺ 2)	1
	¹⁵⁶Eu	β⁻	15.2 d	3.1	395	30
	¹⁵⁷Eu	β⁻	15.2 h	3.0	372	—
Gadolinium	¹⁵⁹Gd	β⁻	18.6 h	0.2	305	6
Terbium	¹⁶¹Tb	β⁻	6.91 d	0.2	155	42
Dysprosium	¹⁶⁵Dy	β⁻	2.33 h	0.1	442	7
Holmium	¹⁶¹Ho	EC	2.48 h	1.8	—	32
	¹⁶⁶Ho	β⁻	1.12 d	0.04	711	29
	¹⁶⁷Ho	β⁻	3.10 h	1.6	188	42
Erbium	¹⁶⁹Er	β⁻	9.40 d	5.0 × 10⁻⁴	100	—
Thulium	¹⁶⁷Tm	EC	9.24 d	1.2	—	126
	¹⁷²Tm	β⁻	2.65 d	0.9	493	39
	¹⁷³Tm	β⁻	8.24 h	1.3	293	16
Ytterbium	¹⁷⁵Yb	β⁻	4.19 d	0.3	127	4
Lutetium	^176mLu	β⁻	3.64 h	0.03	390	39
	¹⁷⁷Lu	β⁻	6.71 d	0.2	133	15
	¹⁷⁹Lu	β⁻	4.59 h	0.1	464	2
Yttrium	⁹⁰Y	β⁻	2.67 d	2.1 × 10⁻³	934	—
Iodine	¹³¹I	β⁻	8.04 d	2.0	182	10

p/e value is total photon energy emitted per decay divided by total electron energy emitted per decay. Mean electron energy is mean energy of Auger and conversion electrons emitted per decay. Corresponding data for ⁹⁰Y and ¹³¹I are given for comparison.