The Discoverers of the Ruthenium Isotopes
Journal Archive
doi: 10.1595/147106711X592448
The Discoverers of the Ruthenium Isotopes
Updated information on the discoveries of the six platinum group metals to 2010
Article Synopsis
This review looks at the discovery and the discoverers of the thirty-eight known ruthenium isotopes with mass numbers from 87 to 124 found between 1931 and 2010. This is the sixth and final review on the circumstances surrounding the discoveries of the isotopes of the six platinum group elements. The first review on platinum isotopes was published in this Journal in October 2000 (1), the second on iridium isotopes in October 2003 (2), the third on osmium isotopes in October 2004 (3), the fourth on palladium isotopes in April 2006 (4) and the fifth on rhodium isotopes in April 2011 (5). An update on the new isotopes of palladium, osmium, iridium and platinum discovered since the previous reviews in this series is also included.
Naturally Occurring Ruthenium
Of the thirty-eight known isotopes of ruthenium, seven occur naturally with the authorised isotopic abundances (6) shown in Table I.
Table I
The Naturally Occurring Isotopes of Ruthenium
Mass number | Isotopic Abundance, % |
---|---|
96Ru | 5.54 |
98Ru | 1.87 |
99Ru | 12.76 |
100Ru | 12.60 |
101Ru | 17.06 |
102Ru | 31.55 |
104Ru | 18.62 |
The isotopes were first detected in 1931 by Aston (7, 8) using a mass spectrograph at the Cavendish Laboratory, Cambridge University, UK. Because of difficult experimental conditions due to the use of poor quality samples, Aston actually only detected six of the isotopes and obtained very approximate percentage abundances. However, he did speculate on the existence of a seventh isotope with mass number 98. In 1943 Ewald (9) of the Aus dem Kaiser Wilhelm-Institut für Chemie, Berlin-Dahlem, Germany, carried out a more refined spectrographic analysis and obtained precision values for the isotopic abundances, including confirming the isotope of mass number 98.
Artificial Ruthenium Isotopes
Early investigations of activities associated with ruthenium tended to lead to half-life values which initially did not appear to be connected to each other. For example, in 1935 Kurchatov, Nemenov and Selinov (10) used slow neutron bombardment to obtain half-lives of 40 seconds, 100 seconds, 11 hours and 75 hours, and in 1936 Livingood (11) used deuteron bombardment to obtain different half-lives of 4 hours, 39 hours, 11 days and 46 days. In 1937, Pool, Cork and Thornton (12) used fast neutron bombardment and obtained activities with half-lives of 24 minutes and 3.6 hours and in 1940 Nishina et al. (13) also used fast neutron bombardment to obtain ruthenium activities of 4 hours and 60 hours and a rhodium activity of 34 hours. However, Nishina et al. (14) later speculated that the 60 hour activity was in reality a mixture of the 4 hour ruthenium and 34 hour rhodium activities plus a further long lived ruthenium activity which had not been identified. They also pointed out that in 1940 Segrè and Seaborg (15) had found a 4 hour half-life ruthenium activity in fission products. In 1938, De Vries and Veldkamp (16) used the different technique of slow neutron bombardment and had identified three activities: a 4 hour activity which they suggested was 103Ru, a 20 hour activity which they suggested was 105Ru and a 45 day half-life activity which they suggested was 105Rh. All of these suggestions were incorrect but it would appear that all of the activities observed with an approximate 4 hour half-life were probably 105Ru and the 46 day activity identified by Livingood and the equal 45 day activity identified by De Vries and Veldkamp were probably 103Ru. None of these observations could be seriously considered as being contenders to the discovery of any isotopes since the discovery criterion of an accurate determination of the atomic mass number had not been met.
Discovery Date
As discussed in previous articles in the present series (1–5), the actual year of discovery is generally considered to be that when the details of the discovery were placed in the public domain such as manuscript dates or conference report dates. However, once again complications arise with the case of internal reports which may not be placed in the public domain until several years later. As with rhodium (5), several ruthenium isotopes were first identified during the highly secretive Plutonium Project of the Second World War which was not actually published until 1951 (17), although much of the information had become available in 1946 in the tables of Siegel (18, 19) or in the 1948 edition of the “Table of Isotopes” (20).
Discovery Acceptance
The discovery criteria used in this series of papers relate to the identification of the ground state and those isomers in which the half-life exceeds one millisecond, except in the very special circumstances where the ground state half-life is itself very short and the half-lives of corresponding isomers are of a similar order. This procedure was adopted to keep the tables succinct by avoiding the inclusion of the exceedingly large number of isomers with half-lives of less than one millisecond which are known for the isotopes of the platinum group elements and which would have greatly complicated the text.
Half-Lives
Selected half-lives used in Table II were generally those accepted in the revised NUBASE database (21) although literature values were used when either these were not available or had been superseded by later determinations.
Table II
The Discoverers of the Ruthenium Isotopes
Mass numbera | Half-life | Decay modes | Year of discovery | Discoverers | References | Notes |
---|---|---|---|---|---|---|
87 | psb | EC + β+ ? | 1994 | Rykaczewski et al. | 22, 23 | |
88 | 1.3 s | EC + β+ | 1994 | Hencheck et al. | 24 | A |
89 | 1.38 s | EC + β+ | 1992 | Mohar et al. | 25, 26 | B |
90 | 12 s | EC + β+ | 1991 | Zhou et al. | 27, 28 | C |
91 | 7.9 s | EC + β+ | 1983 | Komninos, Nolte and Blasi | 29 | |
91m | 7.6 s | EC + β+, IT ? | 1982 | Hagberg et al. | 30 | |
92 | 3.65 min | EC + β+ | 1971 | (a) Arl't et al. (b) De Jesus and Neirinckx | (a) 31, 32 (b) 33 |
|
93 | 59.7 s | EC + β+ | 1955 | Aten Jr. and De Vries-Hamerling | 34 | D |
93m | 10.8 s | EC + β+, IT | 1976 | De Lange et al. | 35 | E |
94 | 51.8 min | EC + β+ | 1952 | Van Der Wiel and Aten Jr. | 36 | |
95 | 1.643 h | EC + β+ | 1948 | Eggen and Pool | 37 | F |
96 | Stable | – | 1931 | Aston | 7, 8 | |
97 | 2.9 d | EC + β+ | 1944 | Sullivan, Sleight and Gladrow | 38, 39 | G |
98 | Stable | – | 1943 | Ewald | 9 | |
99 | Stable | – | 1931 | Aston | 7, 8 | |
100 | Stable | – | 1931 | Aston | 7, 8 | |
101 | Stable | – | 1931 | Aston | 7, 8 | |
102 | Stable | – | 1931 | Aston | 7, 8 | |
103 | 39.25 d | β− | 1944 | (a) Sullivan, Sleight and Gladrow (b) Bohr and Hole | (a) 38, 40 (b) 41 |
H |
103m | 1.69 ms | IT | 1964 | Brandi et al. | 42 | |
104 | Stable | – | 1931 | Aston | 7, 8 | |
105 | 4.44 h | β− | 1944 | (a) Sullivan, Sleight and Gladrow (b) Bohr and Hole | (a) 38, 43 (b) 41 |
H |
106 | 371.8 d | β− | 1946 | (a) Glendenin (b) Grummitt and Wilkinson | (a) 44, 45 (b) 46 |
I |
107 | 3.75 min | β− | 1962 | Pierson, Griffin and Coryell | 47 | J |
108 | 4.55 min | β− | 1955 | Baró, Rey and Seelmann-Eggebert | 48 | |
109 | 34.5 s | β− | 1966 | Griffiths and Fritze | 49, 50 | K |
110 | 11.6 s | β− | 1969 | Wilhelmy et al. | 51, 52 | |
111 | 2.12 s | β− | 1975 | Fettweis and del Marmol | 53 | L |
112 | 1.7 s | β− | 1969 | Wilhelmy et al. | 51, 52 | |
113 | 800 ms | β− | 1988 | Penttilä et al. | 54 | M |
113m | 510 ms | IT ?, β− ? | 1998 | Kurpeta et al. | 55 | |
114 | 540 ms | β− | 1991 | Leino et al. | 56 | |
115 | 318 ms | β− | 1992 | Äystö et al. | 57, 58 | |
115m | 76 ms | IT | 2010 | Kurpeta et al. | 59 | |
116 | 204 ms | β− | 1994 | Bernas et al. | 60 | N |
117 | 142 ms | β− | 1994 | Bernas et al. | 60 | N |
118 | 123 ms | β− | 1994 | Bernas et al. | 60 | N |
119 | psb | β− ? | 1995 | Czajkowski et al. | 61, 62 | |
120 | psb | β− ? | 2010 | Ohnishi et al. | 63 | P |
121 | psb | β− ? | 2010 | Ohnishi et al. | 63 | |
122 | psb | β− ? | 2010 | Ohnishi et al. | 63 | |
123 | psb | β− ? | 2010 | Ohnishi et al. | 63 | |
124 | psb | β− ? | 2010 | Ohnishi et al. | 63 |
a m = isomeric state
b ps = particle stable (resistant to proton and neutron decay)
A | 88Ru | Hencheck et al. (24) only proved that the isotope was particle stable. The half-life was first determined by Wefers et al. in 1999 (64). |
B | 89Ru | Mohar et al. (25, 26) only proved that the isotope was particle stable. The half-life was first determined by Li Zhankui et al. in 1999 (65). |
C | 90Ru | Mohar et al. (25, 26) also claimed the discovery of this isotope in 1992 and appeared to be unaware of the prior discovery by Zhou et al. (27, 28). However they only determined that the isotope was particle stable whereas Zhou et al. had already determined the half-life. |
D | 93Ru | The discovery by Aten Jr. and De Vries-Hamerling (34) is considered to be tentative but was confirmed by Doron and Lanford (66) in 1971. |
E | 93mRu | Doron and Lanford (66) also claimed to have discovered this isomer in 1971 but de Lange et al. (35) could not confirm their half-life of 45 s. |
F | 95Ru | Mock et al. (67) appeared to independently claim the discovery even though their manuscript date was October 1948; the discovery claim by Eggen and Pool (37) had already been published in July 1948. |
G | 97Ru | The 1944 discovery by Sullivan, Sleight and Gladrow (38) was not made public for this isotope until included in the 1946 public report (39). |
H | 103Ru and 105Ru | The 1944 discovery for these isotopes by Sullivan, Sleight and Gladrow (38) was not made public until included in the 1946 table of Siegel (18, 19). |
I | 106Ru | Although produced in 1946, the results of Glendenin (44) were only made public at this time by including in the 1946 table of Siegel (18, 19). |
J | 107Ru | A preliminary identification of this isotope by Glendenin (68, 69) in 1944 was made public in the 1946 table of Siegel (18, 19). |
K | 109Ru | Franz and Herrmann (70) proposed the existence of a 12.9 s half-life isomer but this could not be found by Kaffrell et al. (71). |
L | 111Ru | Franz and Herrmann (70) also tentatively identified this isotope in 1975. |
M | 113Ru | Franz and Herrmann (70) tentatively claimed to have discovered this isotope in 1975 but Penttilä et al. (54) consider that the isotope observed was probably 113Rh. |
N | 116Ru to 118Ru | Bernas et al. (60) only determined that these isotopes were particle stable. The half-lives were first measured by Montes et al. (72) in 2005. |
P | 120Ru | A 1995 claim by Czajkowski et al. (61) to have discovered this isotope was highly preliminary and was not included in the later 1997 report by Bernas et al. (62). Ohnishi et al. (63) detected this isotope in 2010 but did not claim the discovery possibly under the impression that the isotope had already been found but they can be considered to be the actual discoverers. |
An Update on the Discovery and Discoverers of the Platinum Group of Elements
Since the publication of the first four reviews in this series (1–4) a number of new isotopes have been discovered for palladium, osmium, iridium and platinum and the discovery circumstances for these isotopes are listed in Table III. The total number of isotopes for each element and their mass number ranges are now as shown in Table IV.
In addition the half-life of 199Ir was unknown until determined to be 6 seconds by Kurtukian-Nieto (77).
Table III
New Discoveries
Element | Mass numbera | Half-life | Decay mode | Year of discovery | Discoverers | References | Notes |
---|---|---|---|---|---|---|---|
Pd | 125 | psb | β− ? | 2008 | Ohnishi et al. | ||
126 | psb | β− ? | 2008 | Ohnishi et al. | 73 | ||
127 | psb | β− ? | 2010 | Ohnishi et al. | 63 | ||
128 | psb | β− ? | 2010 | Ohnishi et al. | 63 | ||
Os | 161 | 570 μs | α | 2008 | Page et al. | 74 | |
195m | 26 ns | IT | 2002 | Podolyák et al. | 75 | A1 | |
197 | 2.8 min | β− | 2003 | Xu et al. | 76 | ||
198 | psb | β− ? | 2006 | Kurtukian-Nieto et al. | 77, 78 | B1 | |
199 | 5 s | β− | 2005 | Kurtukian-Nieto et al. | 79 | ||
200 | 6 s | β− | 2005 | Kurtukian-Nieto et al. | 79 | ||
201 | psb | β− ? | 2007 | Kurtukian-Nieto | 78 | ||
Ir | 200 | psb | β− ? | 2006 | Kurtukian-Nieto et al. | 77, 78 | B1 |
201 | psb | β− ? | 2006 | Kurtukian-Nieto et al. | 77, 78 | B1 | |
202 | 11 s | β− | 2006 | Kurtukian-Nieto et al. | 77, 78 | B1 | |
203 | psb | β− ? | 2006 | Kurtukian-Nieto et al. | 77, 78 | B1 | |
Pt | 203 | 10.1 s | β− | 2005 | Kurtukian-Nieto et al. | 79 | |
204 | 10.3 s | β− | 2006 | Kurtukian-Nieto et al. | 77, 78 | B1, C1 | |
205 | psb | β− ? | 2010 | Alvarez-Pol et al. | 80 | D1 |
[i]am = isomeric state
[ii]bps = particle stable (resistant to proton and neutron decay)
A1 | Although the ground state of 195Os has not been discovered information on the very high level isomer is included to indicate that the isotope has been observed. |
B1 | Kurtukian-Nieto et al. (77) only showed results in the form of a chart with actual mass numbers being given by Kurtukian-Nieto (78) in 2007. |
C1 | Kurtukian-Nieto et al. (77) only determined the isotope to be particle stable. The half-life was first determined by Morales et al. (81) in 2008. |
D1 | Evidence for this isotope was also given by Benlliure et al. (82). |
Table IV
Total Number of Isotopes and Mass Ranges Known for Each Platinum Group Element to 2010
Element | Number of known isotopes | Known mass number ranges |
---|---|---|
Ru | 38 | 87–124 |
Rh | 38 | 89–126 |
Pd | 38 | 91–128 |
Os | 41 | 161–201 |
Ir | 40 | 164–203 |
Pt | 40 | 166–205 |
Professor Michael Thoennessen
Michael Thoennessen (Figure 1) is a Professor in the Department of Physics & Astronomy at Michigan State University (MSU), USA, and Associate Director at the National Superconducting Cyclotron Laboratory (NSCL) located on the campus of MSU. His main research interest is the study of exotic nuclei far from stability, concentrating on neutron-unbound nuclei beyond the neutron dripline. He performs most of his experiments at NSCL with the Modular Neutron Array (MoNA) – a large-area high efficiency neutron detector (Figure 2). He recently initiated a project to document the discovery of all isotopes. These reviews are currently being published in the journal Atomic Data and Nuclear Data Tables. The detailed description for each isotope has been carried out for about 70% and will be finished next year. Whilst some of the discovery criteria differ from these adopted here, there is generally good agreement as to assigning credit to the discoverers.
The Number of Nuclides
If a nuclide is defined as being a unique combination of protons and neutrons, then the platinum group elements currently include 235 known nuclides out of a total for all elements of about 3200. Of these, 286 are primordial, that is they were present when the Earth was formed and are still present now. The remaining ∼2900 are described for these purposes as being ‘artificial’ radioactive nuclides, since a number of the primordial nuclides are also radioactive but with very long half-lives. There exist in nature a significant number of nuclides other than those of primordial origin due to various radioactive decay modes of naturally occurring thorium and uranium isotopes. The limits on the stability of the nuclides are defined by the proton and neutron drip lines beyond which the nuclides lose particle stability, become unbound and emit protons in the case of the proton drip line and neutrons in the case of the neutron drip line. Nuclides do exist beyond the drip lines but in the case of the light elements the half-lives immediately plunge to very short values. Thoennessen (83) has discussed the difficulties in producing nuclides close to the edges of the drip lines, and whilst for the lighter elements both the proton and neutron drip lines have been reached, only the proton drip line has been approached throughout the Periodic Table. For the medium to heavy elements, a large number of nuclides remain to be discovered before the neutron drip line is reached. Thoennessen and Sherrill (84) predict that up to the presently known limits of the Periodic Table the number of nuclides remaining to be discovered is likely to be at least equal to the number already known. There is optimism that at least 1000 of these will be discovered in the next ten years.
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