Neutrinoless Double β⁺/EC Decays

Table 4

R0𝜈ECEC decay transitions with the final-state spin-parity indicated in the second column and the degeneracy parameters 𝑄−𝐸 in the third column. Also the involved atomic orbitals have been given in the fourth column. The second last column lists the currently available half-life estimates with the references to the 𝑄-value measurement and calculations indicated in the last column.

Transition	𝐽^𝜋𝑓	𝑄−𝐸 [keV]	Orbitals	𝐶^ECEC	References
^74Se→^74Ge	2^+	2.23	L2L3	(0.2−100) × 10^43	[33]
^96Ru→^96Mo	2^+	8.92 (13)	L1L3		[34]
	0^+?	−3.90 (13)	L1L1
^102Pd→^102Ru	2^+	75.26 (36)	KL3		[35]
^106Cd→^106Pd	0^+ ?	8.39	KK	(2.1−5.7) × 10^30	[36]
	(2,3)^−	−0.33 (41)	KL3		[35]
^112Sn→^112Cd	0^+	−4.5	KK	>5.9 × 10^29	[37]
^124Xe→^124Te	0^+ ?	1.86 (15)	KK	(1.7−5.1) × 10^29	[38]
^130Ba→^130Xe	0^+ ?	10.18 (30)	KK		[38]
^136Ce→^136Ba	0^+	−11.67	KK	(3−23) × 10^32	[39]
^144Sm→^144Nd	2^+	171.89 (87)	KL3		[35]
^152Gd→^152Sm	0^+gs	0.91 (18)	KL1	(1.0−1.5) × 10^27	[40, 41]
^156Dy→^156Gd	1^−	0.75 (10)	KL1		[42]
	0^+	0.54 (24)	L1L1		[42]
	2^+	0.04 (10)	M1N3		[42]
^162Er→^162Dy	2^+	2.69 (30)	KL3		[34]
^164Er→^164Dy	0^+gs	6.81 (13)	L1L1	(3.2−5.2) × 10^31	[41, 43]
^168Yb→^168Er	(2^−)	1.52 (25)	M1M3		[34]
^180W→^180Hf	0^+gs	11.24 (27)	KK	(4.0−9.5) × 10^29	[41, 44]