List of levels for 250BK

Author: Y. Akovali | Citation: Nucl. Data Sheets 94,131 (2001) | Cutoff date: 1-Aug-2001

Since the 39.⁹H ²⁵⁴Es α decay and ²⁴⁹Bk(n,γ) data presented in this evaluation are considered as preliminary, level schemes and predominant configuration assignments given here, which are based mostly on these data, should Be taken as tentative, particularly in view of some interpretations that are inconsistent with data.

Assuming the level scheme is correct, the inconsistencies noted here can Be explained by large admixtures of other configurations. See 275.7-d ²⁵⁴Es and 39.³H ²⁵⁴Es α decays and ²⁴⁹Bk(n,γ) data sections for additional remarks.

Theoretical studies:

Fission-barrier properties were calculated by 1977Pr10, 1980Ku14, 1984Oh09, 1984Ku05, 1984Ro23.

For discussions and calculations of Gallagher-Moszkovski splitting, and of odd- and even-spin states’ energy shifts (Newby shifts), see, for example, 1986Ho30, 1986Ho36, 1986So12, 1988Fr16, 1989HoZI, 1994No15.

Q-value: Note: Current evaluation has used the following Q record 1780 4 4969 5 5087 6 5532 19 1995Au04

E(level): From 275.7-d and 39.³H ²⁵⁴Es α decay and from ²⁴⁹Bk(n,γ) reaction studies.

T_1/2(level): Excited states’ half-lives are from 275.7-d and 39.³H ²⁵⁴Es α decay

E(γ): From (n,γ), 276-d and 39.³H ²⁵⁴Es α decays.

I(γ): Relative photon intensities deexciting each level. These branchings are deduced from Iγ’s measured in ²⁵⁴Es α decays.

M(γ): Deduced in ²⁵⁴Es α decays and (n,γ) work.

E(level) (keV)	J^π(level)	T_1/2(level)	E(γ) (keV)	Multipolarity	Conversion Coefficient	Additional Data
34.47	(3-)		34.47	(M1,E2)	18×10²	α=18×10² 16
35.59	(4+)	29 µs 1	1.12	[E1]		B(E1)(W.u.)≈1E-6
35.59	(4+)	29 µs 1	35.59	(M2)	1.287×10⁴	B(M2)(W.u.)≈0.026, α=1.287×10⁴
86	(7+)	213 µs 8	8	[E2]	1.3×10⁶	B(E2)(W.u.)=0.0007 5, α=1.3E6
97.49	(5-)	38 ns 5	61.91	(E1)	0.508	B(E1)(W.u.)=1.25E-5 18, α=0.508
103.83	(1-)		103.83	(M1)	7.47	α=7.47
115.45	(3+)		79.86	(M1)	16.05	α=16.05
125.01	(2-)		90.53	(M1)	11.13	α=11.13
125.01	(2-)		125.01	(M1)	4.38	α=4.38
130.49	(6+)		52.16	(M1+E2)	2.6×10²	α=2.6×10² 20
130.49	(6+)		94.91	(E2)	26.7	α=26.7
137.32	(5-)		57.06	(M1)	42.8	α=42.8
137.32	(5-)		102.84	(E2)	18.4	α=18.4
146.43	(2-)		111.96	(M1)	6.01	α=6.01
146.43	(2-)		146.43	(M1+E2)	8.3	α=8.3 41
148.60	(4+)		70.27	(M1)	23.3	α=23.3
148.60	(4+)		113.01	(M1)	5.85	α=5.85
156	(8+)		70.4 2	(M1+E2)	66	α=66 43
157.39	(3-)		53.59	(E2)	402.8	α=402.8
	(3-)		77.13	(M1)	17.78	α=17.78
	(3-)		122.95	(M1)	4.59	α=4.59
167.09	(6-)		69.60	(M1+E2)	69	α=69 24
175.13	(1+)	42 ns 2	50.12	(E1)	0.882	B(E1)(W.u.)=3.5E-6 7, α=0.882
	(1+)	42 ns 2	71.30	(E1)	0.352	B(E1)(W.u.)=5.6E-6 8, α=0.352
	(1+)	42 ns 2	175.12	[E1+M2]	2.76	B(E1)(W.u.)=2.2E-8 6, B(M2)(W.u.)=0.30 8, α=2.76
E(level) (keV)	J^π(level)	T_1/2(level)	E(γ) (keV)	Multipolarity	Conversion Coefficient	Additional Data
179.99	(3-)		145.56	(M1)	12.9	α=12.9
179.99	(3-)		179.99	(M1+E2)	4.3	α=4.3 27
203.64	(4-)		123.37	(M1)	4.55	α=4.55
203.64	(4-)		169.19	(M1)	8.40	α=8.40
211.82	2+		96.38	(M1)	9.28	α=9.28
	2+		177.36	(E1)	0.145	α=0.145
	2+		211.82	E1	0.0967	α=0.0967
215.94	(0+)		40.82	(M1)	113.7	α=113.7
215.94	(0+)		112.116	(E1)	0.109	α=0.109
236.74	(3+)		121.29	(M1)	4.78	α=4.78
270.46	(4+)		58.64	(E2)	261	α=261
316.46	(5+)		238.14	(M1)	3.21	α=3.21
316.46	(5+)		280.88	(M1)	2.03	α=2.03
369.61	(6+)		239.18	(M1)	3.17	α=3.17
369.61	(6+)		291.36	(M1)	1.81	α=1.81

Q(β-)=1780 keV 4	S(n)= 4970 keV 4	S(p)= 5089 keV 6	Q(α)= 5531 keV SY
Reference: 2012WA38

References:
A	²⁵⁴Es α decay (275.7 d)	B	²⁵⁴Es α decay (39.3 H)
C	²⁴⁹Bk(n,γ):(TENTATIVE)

E(level) (keV)	XREF	J^π(level)	T_1/2(level)	E(γ) (keV)	I(γ)	M(γ)	Final Levels
0.0	A B C	2-	3.212 h 5 % β^- = 100
34.47	A B C	(3-)		34.47		(M1,E2)	0.0	2-
35.59	A B C	(4+)	29 µs 1	1.12S 35.59	100	[E1] (M2)	34.47 0.0	(3-) 2-
78.33	A B C	(5+)		42.74		(M1+E2)	35.59	(4+)
80.26	C	(4-)		45.79 80.26		(M1+E2) (E2)	34.47 0.0	(3-) 2-
86 2	A	(7+)	213 µs 8	8S		[E2]	78.33	(5+)
97.49	A C	(5-)	38 ns 5	61.91		(E1)	35.59	(4+)
103.83	B C	(1-)		103.83		(M1)	0.0	2-
115.45	B C	(3+)		79.86		(M1)	35.59	(4+)
125.01	B C	(2-)		90.53 125.01	100 30 75 30	(M1) (M1)	34.47 0.0	(3-) 2-
130.49	A B C	(6+)		52.16 94.91		(M1+E2) (E2)	78.33 35.59	(5+) (4+)
137.32	A B C	(5-)		57.06 102.84		(M1) (E2)	80.26 34.47	(4-) (3-)
146.43	C	(2-)		111.96 146.43		(M1) (M1+E2)	34.47 0.0	(3-) 2-
148.60	C	(4+)		70.27 113.01		(M1) (M1)	78.33 35.59	(5+) (4+)
156 2	A	(8+)		70.4 2		(M1+E2)	86	(7+)
157.39	C	(3-)		53.59 77.13 122.95		(E2) (M1) (M1)	103.83 80.26 34.47	(1-) (4-) (3-)
167.09	A C	(6-)		69.60		(M1+E2)	97.49	(5-)
175.13	B C	(1+)	42 ns 2	50.12 71.30 175.12	22 3 100 10 6.5 14	(E1) (E1) [E1+M2]	125.01 103.83 0.0	(2-) (1-) 2-
E(level) (keV)	XREF	J^π(level)	T_1/2(level)	E(γ) (keV)	I(γ)	M(γ)	Final Levels
179.99	C	(3-)		145.56 179.99		(M1) (M1+E2)	34.47 0.0	(3-) 2-
190 2	A	(7+)
203.64	C	(4-)		123.37 169.19		(M1) (M1)	80.26 34.47	(4-) (3-)
211.82	B C	2+		36.7S 96.38 177.36 211.82	5.9 7 59 6 100 10	(M1) (E1) E1	175.13 115.45 34.47 0.0	(1+) (3+) (3-) 2-
215.94	C	(0+)		40.82 112.116		(M1) (E1)	175.13 103.83	(1+) (1-)
236.74	B C	(3+)		121.29 202.27		(M1)	115.45 34.47	(3+) (3-)
241 2	A	(9+)		85.1 1		(M1,E2)	156	(8+)
247.9 2	A	(7-)		80.8 1 150 2		(M1,E2)	167.09 97.49	(6-) (5-)
270.46	B C	(4+)		58.64 235.98		(E2)	211.82 34.47	2+ (3-)
298 2	B
316 3	B	(5+)
316.46	C	(5+)		238.14 280.88		(M1) (M1)	78.33 35.59	(5+) (4+)
325 2	A			233 2 ? 249 2	32 4 100 16		97.49 78.33	(5-) (5+)
333 2	A
≈341	A
369.61	C	(6+)		239.18 291.36		(M1) (M1)	130.49 78.33	(6+) (5+)
406	C	(6+)
413 3	A			316 2			97.49	(5-)
E(level) (keV)	XREF	J^π(level)	T_1/2(level)	E(γ) (keV)	I(γ)	M(γ)	Final Levels
471 2	A			304 2			167.09	(6-)
526	C
527 20	A
552	C
566	C

E(level)	E(gamma)	Comments
211.82	36.7	E(γ): from level scheme.
236.74	202.27	E(γ): deduced from level energies shown in 1982HoZE. γ energy was not given in the decay scheme of 1982HoZE.

E(level)	J^π(level)	T_1/2(level)	Comments
0.0	2-	3.212 h 5 % β^- = 100	Among the available Nilsson orbitals, analogy to ²⁵¹Bk and ²⁵¹Cf for the proton and neutron states suggests that probable configuration is 2-,(p 3/2[521]+n 1/2[620]). E(level): Among the available Nilsson orbitals, analogy to ²⁵¹Bk and ²⁵¹Cf for the proton and neutron states suggests that probable configuration is 2-,(p 3/2[521]+n 1/2[620]). K=2.
34.47	(3-)		E(level): K=2.
35.59	(4+)	29 µs 1	E(level): K=4.
78.33	(5+)		E(level): K=4.
80.26	(4-)		E(level): K=2.
86	(7+)	213 µs 8	E(level): K=7.
97.49	(5-)	38 ns 5	E(level): K=5.
103.83	(1-)		E(level): K=1.
115.45	(3+)		Another reason for adopting this order is that if the 3⁺ state were at 131.97 keV, the rotational band parameter would Be much too small, assuming the assignment of the 148.60-keV level as the band’s 4⁺ member is correct. E(level): Another reason for adopting this order is that if the 3⁺ state were at 131.97 keV, the rotational band parameter would Be much too small, assuming the assignment of the 148.60-keV level as the band’s 4⁺ member is correct. K=3.
125.01	(2-)		E(level): K=1.
130.49	(6+)		E(level): K=4.
137.32	(5-)		E(level): K=2.
146.43	(2-)		E(level): K=2.
148.60	(4+)		E(level): K=3.
156	(8+)		E(level): K=7.
157.39	(3-)		E(level): K=1.
167.09	(6-)		E(level): K=5.
179.99	(3-)		E(level): K=2.
190	(7+)		E(level): K=4.
203.64	(4-)		E(level): K=1.
211.82	2+		E(level): K=2.
236.74	(3+)		E(level): K=2.
241	(9+)		E(level): K=7.
247.9	(7-)		E(level): K=5.
270.46	(4+)		E(level): K=2.
E(level)	J^π(level)	T_1/2(level)	Comments
316	(5+)		E(level): K=2.
316.46	(5+)		E(level): K=5.
369.61	(6+)		E(level): K=5.
413			E(level): The authors of 1966Mc02 tentatively suggested that the 413-,471- and 527-keV levels might Be members of a rotational band. They may possibly Be the 6⁺, 7⁺ and 8⁺ members of the K=6 band, identified at 406 keV.
471			E(level): The authors of 1966Mc02 tentatively suggested that the 413-,471- and 527-keV levels might Be members of a rotational band. They may possibly Be the 6⁺, 7⁺ and 8⁺ members of the K=6 band, identified at 406 keV.
527			E(level): The authors of 1966Mc02 tentatively suggested that the 413-,471- and 527-keV levels might Be members of a rotational band. They may possibly Be the 6⁺, 7⁺ and 8⁺ members of the K=6 band, identified at 406 keV.