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Precise atomic mass determinations at mass 124
Volume 138B, number 4
PHYSICS LETTERS
19 April 1984
PRECISE ATOMIC MASS DETERMINATIONS AT MASS 124 B.J. HALL 1 R.J. ELLIS, G.R. DYCK, C.A. LANDER, R. BEACH, K.S. SHARMA, ,
R.C. BARBER and H.E. DUCKWORTH Department of Physics, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2 Received 9 January 1984
The Manitoba II high-resolution mass spectrometer has been used to determine eight precise atomic mass differences amongst 1248n, 124Te, 124Xe, 13C37C13 and 54Fe35C12. Precise values have been derived for the double t3-decay energies of 124Xe and 124Sn and for the masses of 124Sn, lZ4Te, 124Xe and 54Fe. The precision of the mass of 124Xe has been improved by a factor of ~150.
In the 1977 atomic mass evaluation [1], the least accurate value for the mass of a stable nuclide was that o f 124Xe. This value was based entirely on early mass spectroscopic work [2] whose accuracy was much inferior to that of current work. This nuclide is also part of the stable isobaric triplet, 124Sn-124Te-124Xe, whose atomic numbers differ by 2. In the light of renewed interest in possible cases of double/3-decay, and the prospect o f a greatly improved value for the mass of 124Xe, we have determined the masses of the members of the triplet at A = 124. The Manitoba II high-resolution mass spectrometer was used to obtain precise values for the spacings of the eight possible doublets that can be formed amongst the ions 124Sn, 124Te, 124Xe, 13C37C13 and 54Fe35C12. These doublets, listed in table 1 and shown schematically in fig. 1, provide the required information to derive "best" values for the atomic mass differences (i.e. the energy involved in double/3-decay) as well as the absolute atomic masses. The 54Fe35C12 peak was included because it increased the number of possible experimental determinations at A = 124 and also provided an absolute mass determination for A = 54. The latter is consistent with a long term goal of making such determinations at a number of strategic locations throughout the mass table [3]. 1 Current address: Department of Nuclear Physics, Weizmann Institute of Science, Rehovot 76-100, Israel. 260
Table 1 New doublet values. Code
Doublet
a
124Re 13C37C13
b c d e f g h
:24Xe-124Te 124Xe-54FeaSC12 124Sn-124Te 124Sn-13C37C13 124Te-13C37C13 124Te-S4Ee35C12 13C37C13 54Fe35C12
a M (in ~u) 4831.15 3076.00 28575.78 2458.51 4210.47 1754.63 25501.65 23744.46
-+ 1.58 -+ 1.78 -+0.99 +- 0.89 +-0.71 -+ 1.26 -+ 2.56 -+ 1.26
A detailed description of the instrument has been given previously [4]. The "visual null" method of peak matching [5], involving a signal averaging technique and an established procedure of calibration [6] to correct for systematic effects, was employed throughout this work. The new values for the doublet spacings are given in table 1. When combined with the auxiliary data from table 2, these values yield the atomic masses and mass differences given in the " i n p u t " column of table 3. As is evident from fig. 1, the new values overdetermine the mass differences. A set o f " b e s t " values has been derived by a least-squares evaluation of the data [7], as shown in table 3. The high degree of self-consistency amongst the measured values is reflected in 0.370-2693/84/$ 03.00 © Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)
Volume 138B, number 4
PHYS1CS LETTERS
124Xe
124Sn
124Te
13C 37C13
19 April 1984
54 Fe 35 CI 2
a
i Light
Heavy
Fig. 1.
Table 2 Auxiliary data a). 35C1 37C1 13C me mass-to-energy conversion
35.968852729-+ 68 u 36.965902624 -+ 105 u 13.003354839-* 17 u 548.58026 ± 21 #u lu = 931.5016 -+ 26 MeV
a) From the 1977 atomic mass evaluation (ref, [1]).
t h e generally small values o f (ri/oi) 2 a n d t h e related value o f t h e r e d u c e d X2. Table 4 includes a c o m p a r i s o n b e t w e e n t h e 1977 a t o m i c mass e v a l u a t i o n [1] a n d the p r e s e n t work. T h e m o s t d r a m a t i c change is t h e i m p r o v e m e n t in t h e precision o f the 124Xe mass f r o m -+150 p u to -+1/m. Also s h o w n in t a b l e 4 are direct c o m p a r i s o n s w i t h previously r e p o r t e d mass s p e c t r o s c o p i c values. F o r 124Sn a n d 124Te ' the a g r e e m e n t w i t h relatively precise values f r o m this l a b o r a t o r y [8] a n d f r o m the University o f M i n n e s o t a [9] is gratifying. F o r 124Xe, t h e disagree-
Table 3 Least-squares adjustment a). Atomic mass or mass difference
Input value (in uu)
124Xe 124Sn 124Te S4Fe 124Xe-124Te 124Sn-124Te
123905893.86 123905273.18 123902817.34 53939612.79 3076,00 2458.51 69966281.24 69963207.11
124Xe S4Fe 124Te-S4Fe
ri b)
Output value (in #u) ± 1.59 ± 0.73 _+1,26 -+ 1,28 _+1,78 ± 0.89 -+ 0.99 -+ 2.56
123905893.26 123905273.84 123902816.37 53939612.05 3076.88 2457.47 69966281.20 69693204.32
(ri/ai) z
(in ~u) ± 0.98 ± 0.65 +- 0.78 ± 0.95 _+1.05 ± 0.72 -+ 0.86 ± 1.06
-0.60 0.66 -0.97 -0.74 0.88 1.04 0.04 -2.79
0.15 0.87 0.59 0.33 0.24 1.37 0.001 1.19
a) x 2 = 4.75. The square-root of the reduced X2 =- [x2/f] 1/2 = 1.09. Expected value: 0.65 -<. [x2/f] 1/2 ~ 1.35. b) ri= output value input value. 261
Volume 138B, number 4
PHYSICS LETTERS
Table 4 Comparison values (in tau).
Table 5 Energy available for double t3-decay (in keV).
Nuclide
This work
za a)
124Sn
123905273.84 ± 0.66
124Te
123902816.37 +- 0.78
124Xe
123905893.26 ± 0.99
S4Fe
53939612.05 ± 0.95
2.8 9.8 -8.6 2.4 -227 -227 -0.05 1.1 66.1
+- 5.0 -+ 8.0 -+ 4.1 _+ 13.0 _+150 ± 60 +- 1.80 ± 5.1 +- 8.2
b) c) b) d) b) e) b) f) g)
a) Here, A = this work - comparison value. b) Ref. [1]. c) Ref. [8]. d) Ref. [91. e) Ref. [21. f) Ref. [10]. g) Ref. [11].
m e n t with the very old, and relatively imprecise value from Minnesota [2], is substantial. In the case o f 54Fe, agreement with b o t h the 1977 mass table [1] and the precise value from the University of Minnesota [10] is e x t r e m e l y good. The agreement with the value o f D e m i r k h a n o v et al. [11] is not good. The i m p r o v e d double ~3-decay energies at A = 124 are given in table 5. With the " o u t p u t " values o f table 5, the theoretical branching ratio for 1241 decaying to 124 Xe, previously given as 0.017%, can be recalculated. Using the m e t h o d o f Merrihue [ 12] and the energy difference of 2.289 MeV obtained from our results, one finds a new ratio o f 0.0007%. This is, of course, still consistent with the upper limit ( < 0.1%) given by Merrihue. Finally, m e n t i o n should be made o f the significance o f the 124Xe-54Fe35C12 doublet measurement. This link between 124Xe and 54Fe extends 70 mass units across the mass table. This crosses two breaks in the " b a c k b o n e " o f the mass table [13], at mass numbers 1 0 3 - 1 0 4 and 1 0 8 - 1 1 0 , and supplies i m p o r t a n t
262
19 April 1984
Transition
This work
124Xe(2/3+)124Te 124Sn(2t3-)124Te
2866.12 +- 1.66 2289.14 + 0.83
This work - MT a) 203.3 ± 139.8 10.7 ± 6.0
a) 1977 Atomic mass evaluation (ref. [1 ]). additional information for these regions. The new doublet determination yields a value for this link of 6 9 9 6 6 2 8 1 . 2 -+ 0.9/au, a value which is significantly different from, and more accurate than, the value det e r m i n e d using data from the 1977 mass table, viz., 6 9 9 6 6 5 0 7 +- 150/~u. The new result will thus provide an i m p o r t a n t constraint on the b a c k b o n e o f the mass table in future least-squares adjustments.
References [ 1 ] A.tt. Wapstra and K. Bos, At. Data Nucl. Data Tables 19 (1977) 177. [2] R.E. Halsted, Phys. Rev. 88 (1952) 666. [3] K.S. Kozier et al., Can. J. Phys. 57 (1979) 266. [4] R.C. Barber et al., Rev. Sci. Instrum. 42 (1971) 1. [5] K.S. Kozier et al., Can. J. Phys. 58 (1980) 1311. [6] F.C.G. Southon, J.O. Meredith, R.C. Barber and H.E. Duckworth, Can. J. Phys. 55 (1977) 383. [7] J.O. Meredith and R.C. Barber, Can. J. Phys. 50 (1972) 1195. [8] R.C. Barber et al., Can. J. Phys. 40 (1963) 1496. [9] R.A. Damerow, R.R. Ries and W.H. Johnson, Phys. Rev. 132 (1963) 1673. [10] K.S. Quisenberry, T.T. Scolman and A.O. Nier, Phys. Rev. 104 (1956) 461. [ 11 ] R.A. Demirkhanov, V.V. Dorokhov and M.I. Dzkuya, Atomic masses and fundamental constants, Vol. 4, eds. J.H. Sanders and A.H. Wapstra (Plenum, Ncw York, 1972). [12] C.M. Merrihue, Phys. Rev. 124 (1961) 208. [13] A.tt. Wapstra and K. Bos, At. Data Nucl. Data Tables 2O (1977) 1.
PHYSICS LETTERS
19 April 1984
PRECISE ATOMIC MASS DETERMINATIONS AT MASS 124 B.J. HALL 1 R.J. ELLIS, G.R. DYCK, C.A. LANDER, R. BEACH, K.S. SHARMA, ,
R.C. BARBER and H.E. DUCKWORTH Department of Physics, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2 Received 9 January 1984
The Manitoba II high-resolution mass spectrometer has been used to determine eight precise atomic mass differences amongst 1248n, 124Te, 124Xe, 13C37C13 and 54Fe35C12. Precise values have been derived for the double t3-decay energies of 124Xe and 124Sn and for the masses of 124Sn, lZ4Te, 124Xe and 54Fe. The precision of the mass of 124Xe has been improved by a factor of ~150.
In the 1977 atomic mass evaluation [1], the least accurate value for the mass of a stable nuclide was that o f 124Xe. This value was based entirely on early mass spectroscopic work [2] whose accuracy was much inferior to that of current work. This nuclide is also part of the stable isobaric triplet, 124Sn-124Te-124Xe, whose atomic numbers differ by 2. In the light of renewed interest in possible cases of double/3-decay, and the prospect o f a greatly improved value for the mass of 124Xe, we have determined the masses of the members of the triplet at A = 124. The Manitoba II high-resolution mass spectrometer was used to obtain precise values for the spacings of the eight possible doublets that can be formed amongst the ions 124Sn, 124Te, 124Xe, 13C37C13 and 54Fe35C12. These doublets, listed in table 1 and shown schematically in fig. 1, provide the required information to derive "best" values for the atomic mass differences (i.e. the energy involved in double/3-decay) as well as the absolute atomic masses. The 54Fe35C12 peak was included because it increased the number of possible experimental determinations at A = 124 and also provided an absolute mass determination for A = 54. The latter is consistent with a long term goal of making such determinations at a number of strategic locations throughout the mass table [3]. 1 Current address: Department of Nuclear Physics, Weizmann Institute of Science, Rehovot 76-100, Israel. 260
Table 1 New doublet values. Code
Doublet
a
124Re 13C37C13
b c d e f g h
:24Xe-124Te 124Xe-54FeaSC12 124Sn-124Te 124Sn-13C37C13 124Te-13C37C13 124Te-S4Ee35C12 13C37C13 54Fe35C12
a M (in ~u) 4831.15 3076.00 28575.78 2458.51 4210.47 1754.63 25501.65 23744.46
-+ 1.58 -+ 1.78 -+0.99 +- 0.89 +-0.71 -+ 1.26 -+ 2.56 -+ 1.26
A detailed description of the instrument has been given previously [4]. The "visual null" method of peak matching [5], involving a signal averaging technique and an established procedure of calibration [6] to correct for systematic effects, was employed throughout this work. The new values for the doublet spacings are given in table 1. When combined with the auxiliary data from table 2, these values yield the atomic masses and mass differences given in the " i n p u t " column of table 3. As is evident from fig. 1, the new values overdetermine the mass differences. A set o f " b e s t " values has been derived by a least-squares evaluation of the data [7], as shown in table 3. The high degree of self-consistency amongst the measured values is reflected in 0.370-2693/84/$ 03.00 © Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)
Volume 138B, number 4
PHYS1CS LETTERS
124Xe
124Sn
124Te
13C 37C13
19 April 1984
54 Fe 35 CI 2
a
i Light
Heavy
Fig. 1.
Table 2 Auxiliary data a). 35C1 37C1 13C me mass-to-energy conversion
35.968852729-+ 68 u 36.965902624 -+ 105 u 13.003354839-* 17 u 548.58026 ± 21 #u lu = 931.5016 -+ 26 MeV
a) From the 1977 atomic mass evaluation (ref, [1]).
t h e generally small values o f (ri/oi) 2 a n d t h e related value o f t h e r e d u c e d X2. Table 4 includes a c o m p a r i s o n b e t w e e n t h e 1977 a t o m i c mass e v a l u a t i o n [1] a n d the p r e s e n t work. T h e m o s t d r a m a t i c change is t h e i m p r o v e m e n t in t h e precision o f the 124Xe mass f r o m -+150 p u to -+1/m. Also s h o w n in t a b l e 4 are direct c o m p a r i s o n s w i t h previously r e p o r t e d mass s p e c t r o s c o p i c values. F o r 124Sn a n d 124Te ' the a g r e e m e n t w i t h relatively precise values f r o m this l a b o r a t o r y [8] a n d f r o m the University o f M i n n e s o t a [9] is gratifying. F o r 124Xe, t h e disagree-
Table 3 Least-squares adjustment a). Atomic mass or mass difference
Input value (in uu)
124Xe 124Sn 124Te S4Fe 124Xe-124Te 124Sn-124Te
123905893.86 123905273.18 123902817.34 53939612.79 3076,00 2458.51 69966281.24 69963207.11
124Xe S4Fe 124Te-S4Fe
ri b)
Output value (in #u) ± 1.59 ± 0.73 _+1,26 -+ 1,28 _+1,78 ± 0.89 -+ 0.99 -+ 2.56
123905893.26 123905273.84 123902816.37 53939612.05 3076.88 2457.47 69966281.20 69693204.32
(ri/ai) z
(in ~u) ± 0.98 ± 0.65 +- 0.78 ± 0.95 _+1.05 ± 0.72 -+ 0.86 ± 1.06
-0.60 0.66 -0.97 -0.74 0.88 1.04 0.04 -2.79
0.15 0.87 0.59 0.33 0.24 1.37 0.001 1.19
a) x 2 = 4.75. The square-root of the reduced X2 =- [x2/f] 1/2 = 1.09. Expected value: 0.65 -<. [x2/f] 1/2 ~ 1.35. b) ri= output value input value. 261
Volume 138B, number 4
PHYSICS LETTERS
Table 4 Comparison values (in tau).
Table 5 Energy available for double t3-decay (in keV).
Nuclide
This work
za a)
124Sn
123905273.84 ± 0.66
124Te
123902816.37 +- 0.78
124Xe
123905893.26 ± 0.99
S4Fe
53939612.05 ± 0.95
2.8 9.8 -8.6 2.4 -227 -227 -0.05 1.1 66.1
+- 5.0 -+ 8.0 -+ 4.1 _+ 13.0 _+150 ± 60 +- 1.80 ± 5.1 +- 8.2
b) c) b) d) b) e) b) f) g)
a) Here, A = this work - comparison value. b) Ref. [1]. c) Ref. [8]. d) Ref. [91. e) Ref. [21. f) Ref. [10]. g) Ref. [11].
m e n t with the very old, and relatively imprecise value from Minnesota [2], is substantial. In the case o f 54Fe, agreement with b o t h the 1977 mass table [1] and the precise value from the University of Minnesota [10] is e x t r e m e l y good. The agreement with the value o f D e m i r k h a n o v et al. [11] is not good. The i m p r o v e d double ~3-decay energies at A = 124 are given in table 5. With the " o u t p u t " values o f table 5, the theoretical branching ratio for 1241 decaying to 124 Xe, previously given as 0.017%, can be recalculated. Using the m e t h o d o f Merrihue [ 12] and the energy difference of 2.289 MeV obtained from our results, one finds a new ratio o f 0.0007%. This is, of course, still consistent with the upper limit ( < 0.1%) given by Merrihue. Finally, m e n t i o n should be made o f the significance o f the 124Xe-54Fe35C12 doublet measurement. This link between 124Xe and 54Fe extends 70 mass units across the mass table. This crosses two breaks in the " b a c k b o n e " o f the mass table [13], at mass numbers 1 0 3 - 1 0 4 and 1 0 8 - 1 1 0 , and supplies i m p o r t a n t
262
19 April 1984
Transition
This work
124Xe(2/3+)124Te 124Sn(2t3-)124Te
2866.12 +- 1.66 2289.14 + 0.83
This work - MT a) 203.3 ± 139.8 10.7 ± 6.0
a) 1977 Atomic mass evaluation (ref. [1 ]). additional information for these regions. The new doublet determination yields a value for this link of 6 9 9 6 6 2 8 1 . 2 -+ 0.9/au, a value which is significantly different from, and more accurate than, the value det e r m i n e d using data from the 1977 mass table, viz., 6 9 9 6 6 5 0 7 +- 150/~u. The new result will thus provide an i m p o r t a n t constraint on the b a c k b o n e o f the mass table in future least-squares adjustments.
References [ 1 ] A.tt. Wapstra and K. Bos, At. Data Nucl. Data Tables 19 (1977) 177. [2] R.E. Halsted, Phys. Rev. 88 (1952) 666. [3] K.S. Kozier et al., Can. J. Phys. 57 (1979) 266. [4] R.C. Barber et al., Rev. Sci. Instrum. 42 (1971) 1. [5] K.S. Kozier et al., Can. J. Phys. 58 (1980) 1311. [6] F.C.G. Southon, J.O. Meredith, R.C. Barber and H.E. Duckworth, Can. J. Phys. 55 (1977) 383. [7] J.O. Meredith and R.C. Barber, Can. J. Phys. 50 (1972) 1195. [8] R.C. Barber et al., Can. J. Phys. 40 (1963) 1496. [9] R.A. Damerow, R.R. Ries and W.H. Johnson, Phys. Rev. 132 (1963) 1673. [10] K.S. Quisenberry, T.T. Scolman and A.O. Nier, Phys. Rev. 104 (1956) 461. [ 11 ] R.A. Demirkhanov, V.V. Dorokhov and M.I. Dzkuya, Atomic masses and fundamental constants, Vol. 4, eds. J.H. Sanders and A.H. Wapstra (Plenum, Ncw York, 1972). [12] C.M. Merrihue, Phys. Rev. 124 (1961) 208. [13] A.tt. Wapstra and K. Bos, At. Data Nucl. Data Tables 2O (1977) 1.