List of levels for 156EU

Author: C. W. Reich | Citation: Nucl. Data Sheets 113, 2537 (2012) | Cutoff date: 1-Mar-2012

Data are primarily from the ¹⁵³Eu(3n,γ) studies (1991Ba06). Several of the same levels are observed in the β^- decay of ¹⁵⁶Sm (1966Ha26 and others), and three levels reported from the ¹⁵⁴Eu(t,p) reaction.

Some model and theory calculations of possible interest:

1988Fr16: Survey of the properties of K=0 bands in strongly deformed nuclides.

1989HoZI: Empirical study of Newby energy shifts.

1990Af03: Interpretation of the level schemes of the Eu isotopes in terms of octupole deformation.

1992No04: Discussion of the ¹⁵⁶Eu level scheme. Authors conclude that there is no evidence for parity doublets and, hence, for octupole deformation.

1994No15: Thorough discussion of the residual p-n interaction in odd-odd nuclei.

1998Ja07: An excellent survey of nuclear-structure data for the odd-odd nuclides in the region from α=144 through α=194.

Considerable discussion of the level structure of the odd-odd Eu isotopes in terms of reflection asymmetry (e.g., octupole deformation) has appeared in the literature. 1990Af03 have interpreted the data on ¹⁵³Eu through ¹⁵⁶Eu in terms of octupole deformation, deducing values of the octupole-deformation parameter, β₃. In their capture gamma-ray study, 1991Ba06 interpret some of the bands as being parity doublets. From Δ<r²> data for Eu isotopes from α=151 through α=159, however, 1990AlZK conclude that, while octupole deformation is likely present in ¹⁵²Eu and ¹⁵⁴Eu, it is not present in ¹⁵⁶Eu. In their review of the odd-odd nuclides, 1998Ja07 state that present theoretical results are not consistent with octupole deformation in ¹⁵⁶Eu. In the present evaluation, the evaluator has not used the ideas of reflection asymmetry to describe the ¹⁵⁶Eu levels.

Levels: 1991Ba06 rely heavily on those two-quasiparticle states expected to be among the lowest-lying in ¹⁵⁶Eu to assign configurations to the proposed bandheads.

Levels: From model calculations, 1991Ba06 give the computed mixing of configurations for each level. Some of the significant mixtures are noted for the associated bands or levels.

E(level): From the ¹⁵³Eu(3n,γ) data, except two values from the ¹⁵⁴Eu(t,p) reaction.

T_1/2(level): For excited states, from ¹⁵⁶Sm decay (1968An09).

E(γ): From the ¹⁵³Eu(3n,γ) data. Other: ¹⁵⁶Sm β^- decay.

I(γ): From the ¹⁵³Eu(3n,γ) data, unless otherwise noted. Other: ¹⁵⁶Sm β^- decay.

M(γ): From ce data from ¹⁵³Eu(3n,γ) data primarily and ¹⁵⁶Sm β^- decay.

E(level) (keV)	J^π(level)	T_1/2(level)	E(γ) (keV)	Multipolarity	Conversion Coefficient	Additional Data
22.5176	1+		22.525 6	M1	22.6	α=22.6
47.6728	2+		25.1550 5	(M1)	16.31	α=16.31
87.4897	1-	12.0 ns 3	39.7805 4	[E1]	0.606	α=0.606
	1-	12.0 ns 3	64.9725 4	E1	0.900	B(E1)(W.u.)=4.28E-6 +42-15, α=0.900
	1-	12.0 ns 3	87.4897 3	E1	0.407	B(E1)(W.u.)=1.83E-5 +17-6, α=0.407
103.5942	3+		55.9208 6	M1	9.88	α=9.88
125.4568	2-		37.9681 7	M1	4.82	α=4.82
125.4568	2-		102.9361 15	E1	0.262	α=0.262
145.6816	5+		42.0879 8	E2	76.6	α=76.6
159.7111	4+		56.1179 20	M1	9.78	α=9.78
159.7111	4+		112.0381 13	[E2]	1.607	α=1.607
175.1500	4+		29.478 5	E2	444	α=444
	4+		71.5555 5	M1	4.84	α=4.84
	4+		127.478 3	[E2]	1.015	α=1.015
184.1966	3-		58.7402 6	M1	8.58	α=8.58
184.1966	3-		136.5234 29	E1	0.1222	α=0.1222
214.9306	4-		39.7805 4	E1	0.606	α=0.606
217.7761	0-		195.2586 15	E1	0.0467	α=0.0467
250.1646	5+		90.4564 18	M1	2.46	α=2.46
250.1646	5+		146.563 4	E2	0.622	α=0.622
258.1440	4-		73.9501 14	M1	4.40	α=4.40
	4-		132.6885 23	E2	0.881	α=0.881
	4-		154.5454 20	E1	0.0874	α=0.0874
260.1834	4+		85.0345 15	M1	2.94	α=2.94
	4+		110.5106 8	E1	0.217	α=0.217
	4+		114.5018 16	M1	1.253	α=1.253
E(level) (keV)	J^π(level)	T_1/2(level)	E(γ) (keV)	Multipolarity	Conversion Coefficient	Additional Data
266.947	1-		219.277 3	E1	0.0344	α=0.0344
268.7468	2-		165.1527 7	E1	0.0734	α=0.0734
268.7468	2-		246.223 4	E1	0.0254	α=0.0254
268.7478	5+		93.5972 12	M1	2.23	α=2.23
291.3037	1+	≤ 0.2 ns	165.8452 24	E1	0.0723	B(E1)(W.u.)≥7.4E-5, α=0.0723
	1+	≤ 0.2 ns	203.818 3	E1	0.0417	B(E1)(W.u.)≥6.7E-5, α=0.0417
	1+	≤ 0.2 ns	244.0 8	[M1,E2]	0.132	α=0.132 21
	1+	≤ 0.2 ns	268.5 8	[M1,E2]	0.100	α=0.100 18
	1+	≤ 0.2 ns	291.0 8	[M1]	0.0954	B(M1)(W.u.)≥2.8×10^-4, α=0.0954 15
313.0984	5-		167.4175 13	E1	0.0705	α=0.0705
324.6951	2+		140.4983 8	E1	0.1130	α=0.1130
	2+		237.218 6	E1	0.0280	α=0.0280
	2+		302.177 7	M1	0.0863	α=0.0863
343.3202	3-		183.6048 23	E1	0.0550	α=0.0550
343.3202	3-		295.6528 26	E1	0.0158	α=0.0158 9
353.4406	3-		138.5097 5	M1	0.731	α=0.731
353.4406	3-		178.2918 11	E1	0.0595	α=0.0595
368.5352	(5-)		193.3852 26	E1	0.0479	α=0.0479
368.5352	(5-)		218.885 7	M1	0.205	α=0.205
375.3660	3+		117.2242 20	E1	0.185	α=0.185
375.3660	3+		249.900 4	E1	0.0244	α=0.0244
386.3223	4-		136.1584 13	E1	0.1231	α=0.1231
386.3223	4-		282.717 5	E1	0.0178	α=0.0178
434.2302	3-		80.7893 28	M1	3.41	α=3.41
	3-		174.0466 19	E1	0.0635	α=0.0635
	3-		259.082 5	E1	0.0223	α=0.0223
E(level) (keV)	J^π(level)	T_1/2(level)	E(γ) (keV)	Multipolarity	Conversion Coefficient	Additional Data
435.5835	4-		220.6563 24	M1	0.201	α=0.201
435.5835	4-		260.425 7	E1	0.0220	α=0.0220
441.635	4+		257.438 7	E1	0.0226	α=0.0226
513.2906	1-		244.540 3	M1	0.1521	α=0.1521
	1-		295.517 6	M1	0.0915	α=0.0915
	1-		387.863 12	E2	0.0270	α=0.0270
	1-		425.808 9	M1	0.0352	α=0.0352

Q(β-)=2452 keV 3	S(n)= 6336 keV 3	S(p)= 7181 keV 4	Q(α)= -1.25×10³ keV 3
S(2n)= 14487 keV 3	S(2p)= 1.615×10⁴ keV 4
Reference: 2017WA10

E(level) (keV)	XREF	J^π(level)	T_1/2(level)	E(γ) (keV)	I(γ)	M(γ)	Final Levels
0.0	A B	0+	15.19 d 8 % β^- = 100
22.5176 5	A B	1+		22.525 6	100	M1	0.0	0+
47.6728 7	A B	2+		25.1550 5	100	(M1)	22.5176	1+
87.4897 3	A B	1-	12.0 ns 3	39.7805 4 64.9725 4 87.4897 3	<6 7.8 9 100 3	[E1] E1 E1	47.6728 22.5176 0.0	2+ 1+ 0+
103.5942 8	A	3+		55.9208 6	100	M1	47.6728	2+
125.4568 7	A B	2-		37.9681 7 102.9361 15	100 8 46 11	M1 E1	87.4897 22.5176	1- 1+
145.6816 11	A	5+		42.0879 8	100	E2	103.5942	3+
149.6725 16	A	5-		3.99S		[E1]	145.6816	5+
159.7111 12	A	4+		56.1179 20 112.0381 13	100 13 14.6 18	M1 [E2]	103.5942 47.6728	3+ 2+
175.1500 10	A	4+		29.478 5 71.5555 5 127.478 3	100 7 9.4 20	E2 M1 [E2]	145.6816 103.5942 47.6728	5+ 3+ 2+
184.1966 8	A	3-		58.7402 6 136.5234 29	100 8 26 7	M1 E1	125.4568 47.6728	2- 2+
214.9306 10	A	4-		39.7805 4	100	E1	175.1500	4+
217.7761 15	A	0-		195.2586 15	100	E1	22.5176	1+
250.1646 19	A	5+		90.4564 18 146.563 4	100 16 17 4	M1 E2	159.7111 103.5942	4+ 3+
258.1440 12	A	4-		73.9501 14 132.6885 23 154.5454 20	100 8 17 4 69 9	M1 E2 E1	184.1966 125.4568 103.5942	3- 2- 3+
260.1834 14	A	4+		85.0345 15 110.5106 8 114.5018 16	18 3 100 3 14.8 17	M1 E1 M1	175.1500 149.6725 145.6816	4+ 5- 5+
266.947 3	A B	1-		219.277 3 266.937 6	100 7 38 7	E1	47.6728 0.0	2+ 0+
E(level) (keV)	XREF	J^π(level)	T_1/2(level)	E(γ) (keV)	I(γ)	M(γ)	Final Levels
268.7468 11	A	2-		165.1527 7 246.223 4	40 3 100 10	E1 E1	103.5942 22.5176	3+ 1+
268.7478 15 ?	A	5+		93.5972 12 ?	100	M1	175.1500	4+
291.3037 20	A B	1+	≤ 0.2 ns	165.8452 24 203.818 3 244.0 8 268.5 8 291.0 8	60 10 100 80 10 4 11 4 13 5	E1 E1 [M1,E2] [M1,E2] [M1]	125.4568 87.4897 47.6728 22.5176 0.0	2- 1- 2+ 1+ 0+
313.0984 16	A	5-		137.9447 29 167.4175 13	54 6 100 18	E1	175.1500 145.6816	4+ 5+
324.6951 11	A	2+		140.4983 8 237.218 6 302.177 7	33 5 100 15 19.8 19	E1 E1 M1	184.1966 87.4897 22.5176	3- 1- 1+
343.3202 19	A	3-		183.6048 23 295.6528 26	39 4 100 11	E1 E1	159.7111 47.6728	4+ 2+
353.4406 11	A	3-		138.5097 5 178.2918 11	38.9 17 100 8	M1 E1	214.9306 175.1500	4- 4+
368.5352 19	A	(5-)		99.7855 20 193.3852 26 218.885 7	50 12 88 13 100 15	E1 M1	268.7478 175.1500 149.6725	5+ 4+ 5-
375.3660 20	A	3+		117.2242 20 191.177 13 249.900 4	15 3 5.0 9 100 19	E1 E1	258.1440 184.1966 125.4568	4- 3- 2-
386.3223 22	A	4-		43.0076 8 136.1584 13 282.717 5	45 6 16.1 24 100 11	E1 E1	343.3202 250.1646 103.5942	3- 5+ 3+
434.2302 19	A C	3-		80.7893 28 174.0466 19 259.082 5	74 16 100 13 52 10	M1 E1 E1	353.4406 260.1834 175.1500	3- 4+ 4+
435.5835 20	A	4-		82.1396 28 220.6563 24 260.425 7	24 5 100 11 75 9	M1 E1	353.4406 214.9306 175.1500	3- 4- 4+
E(level) (keV)	XREF	J^π(level)	T_1/2(level)	E(γ) (keV)	I(γ)	M(γ)	Final Levels
441.635 7	A	4+		257.438 7	100	E1	184.1966	3-
513.2906 28	A	1-		244.540 3 295.517 6 387.863 12 425.808 9	97 19 100 8 28 4 90 8	M1 M1 E2 M1	268.7468 217.7761 125.4568 87.4897	2- 0- 2- 1-
524 15	C	(4-)
675 16	C

E(level)	E(gamma)	Comments
87.4897	39.7805	E(γ): Multiply placed I(γ): Most of the intensity of this doublet is placed elsewhere in the level scheme (see the discussion in the ¹⁵³Eu(3n,γ) data set).
149.6725	3.99	E(γ): Computed from level energies. Placement deduced to explain decay of 149 level (1991Ba06).
159.7111	112.0381	M(γ): Mult=M1,E2 from ce data, but placement requires E2
175.1500	127.478	M(γ): Mult=M1,E2 from ce data, but placement requires E2
214.9306	39.7805	E(γ): Multiply placed
386.3223	43.0076	I(γ): If this placement is correct, the intensity is too large (1991Ba06).

References:
A	¹⁵³Eu(3n,γ)	B	¹⁵⁶Sm β^- decay
C	¹⁵⁴Eu(t,p)

E(level)	J^π(level)	T_1/2(level)	Comments
0.0	0+	15.19 d 8 % β^- = 100	Δ<r²>(¹⁵⁶Eu-¹⁵¹Eu)=0.72~fm² 4, from collinear LASER spectroscopy (1985Al06 and, from the same group, 1986Al33). For \|l, which is≈Δ<r²>, 1990Al34 report \|l(¹⁵⁶Eu)-\|l(¹⁵¹Eu)=0.693 fm² 7, from resonance ionization spectroscopy. From their compilation of optical isotope-shift data, 1987Au06 report \|l(¹⁵⁶Eu)-\|l(¹⁵¹Eu)=0.63~fm² 4. E(level): Δ<r²>(¹⁵⁶Eu-¹⁵¹Eu)=0.72~fm² 4, from collinear LASER spectroscopy (1985Al06 and, from the same group, 1986Al33). For \|l, which is≈Δ<r²>, 1990Al34 report \|l(¹⁵⁶Eu)-\|l(¹⁵¹Eu)=0.693 fm² 7, from resonance ionization spectroscopy. From their compilation of optical isotope-shift data, 1987Au06 report \|l(¹⁵⁶Eu)-\|l(¹⁵¹Eu)=0.63~fm² 4. K^π=0⁺ g.s. band. configuration=π5/2[413]-ν5/2[642]. For.
22.5176	1+		E(level): K^π=0⁺ g.s. band. configuration=π5/2[413]-ν5/2[642]. For.
47.6728	2+		E(level): K^π=0⁺ g.s. band. configuration=π5/2[413]-ν5/2[642]. For.
87.4897	1-	12.0 ns 3	E(level): K^π=1- band. configuration=π5/2[413]-ν3/2[521].
103.5942	3+		E(level): K^π=0⁺ g.s. band. configuration=π5/2[413]-ν5/2[642]. For.
125.4568	2-		E(level): K^π=1- band. configuration=π5/2[413]-ν3/2[521].
145.6816	5+		E(level): K^π=5⁺ bandhead. configuration=π5/2[413]+ν5/2[642].
149.6725	5-		E(level): K^π=5- bandhead. configuration=π5/2[532]+ν5/2[642].
159.7111	4+		E(level): K^π=0⁺ g.s. band. configuration=π5/2[413]-ν5/2[642]. For.
175.1500	4+		E(level): K^π=4⁺ band. configuration=π5/2[532]+ν3/2[521].
184.1966	3-		E(level): K^π=1- band. configuration=π5/2[413]-ν3/2[521].
214.9306	4-		E(level): K^π=4- band. configuration=π5/2[413]+ν3/2[521].
217.7761	0-		E(level): K^π=0- band. configuration=π5/2[532]-ν5/2[642].
250.1646	5+		E(level): K^π=0⁺ g.s. band. configuration=π5/2[413]-ν5/2[642]. For.
258.1440	4-		E(level): K^π=1- band. configuration=π5/2[413]-ν3/2[521].
260.1834	4+		E(level): K^π=4⁺ bandhead. configuration=π3/2[411]+ν5/2[642].
266.947	1-		E(level): K^π=0- band. configuration=π5/2[532]-ν5/2[642].
268.7468	2-		E(level): K^π=0- band. configuration=π5/2[532]-ν5/2[642].
268.7478	5+		E(level): K^π=4⁺ band. configuration=π5/2[532]+ν3/2[521].
291.3037	1+	≤ 0.2 ns	E(level): K^π=1⁺ band. configuration=π5/2[532]-ν3/2[521].
313.0984	5-		E(level): K^π=4- band. configuration=π5/2[413]+ν3/2[521].
324.6951	2+		E(level): K^π=1⁺ band. configuration=π5/2[532]-ν3/2[521].
343.3202	3-		E(level): K^π=0- band. configuration=π5/2[532]-ν5/2[642].
353.4406	3-		E(level): K^π=3- band. configuration=π3/2[411]+ν3/2[521].
368.5352	(5-)		E(level): K^π=5- band. configuration=π5/2[413]+ν5/2[523]. 1991Ba06.
E(level)	J^π(level)	T_1/2(level)	Comments
375.3660	3+		E(level): K^π=1⁺ band. configuration=π5/2[532]-ν3/2[521].
386.3223	4-		E(level): K^π=0- band. configuration=π5/2[532]-ν5/2[642].
434.2302	3-		XREF: C(448). E(level): K^π=3- band. configuration=π5/2[413]-ν11/2[505].
435.5835	4-		E(level): K^π=3- band. configuration=π3/2[411]+ν3/2[521].
441.635	4+		E(level): K^π=1⁺ band. configuration=π5/2[532]-ν3/2[521].
513.2906	1-		Assigned as a member of a K^π=0- band by 1991Ba06 (in ¹⁵³Eu(3n,γ)). See the discussion of this point in the ¹⁵³Eu(3n,γ) data set. E(level): Assigned as a member of a K^π=0- band by 1991Ba06 (in ¹⁵³Eu(3n,γ)). See the discussion of this point in the ¹⁵³Eu(3n,γ) data set.
524	(4-)		E(level): K^π=3- band. configuration=π5/2[413]-ν11/2[505].