Rutherfordium

Rutherfordium, Rf, is the name of element 104. Wikipedia has an article which provides a lot of information about the element.  This article will focus on things Wikipedia does not stress: heavy isotopes and formation.

Half-lives of Rf isotopes aren't predicted to exceed 3 hrs. One such isotope, ²⁶⁷Rf has a measured half-life of 2.5 hrs. The longer-lived isotopes may survive, in principle, up to a month after a supernova, neutron star merger, or other event leads to its formation. This is long enough for Rf to become part of supernova or kilonova (neutron star merger) remnants.

No Rf isotopes survive long enough to become cool enough to interact chemically outside the laboratory.

NUCLEAR PROPERTIES

INFORMATION SOURCES

Japan Atomic Energy Agency (JAEA) maintains an on-line chart of nuclides which includes decay properties of many predicted nuclides⁽¹⁾ - unlike charts published by Korea Atomic Energy Research Institute (KAERI) or the (U.S.) National Nuclear Data Center (NNDC). This chart gives separate numerical values for partial half-lives against fission, beta emission (both b^- and b⁺), and alpha emission. This reference provides the most focused look at the most significant predicted Rf isotopes.

An independent resource is provided by the U.S.'s Los Alamos National Laboratory (LANL) in interactive tables of contains tabulated partial half-life data for alpha and beta decay⁽²⁾ for numerous nuclides. The great weakness of this source is that it does not consider fission.

A third source describes decay properties of a large number of nuclides⁽³⁾. Half-life data in this source are presented via color, which makes specifying a value within an order of magnitude difficult. In addition, only the dominant decay mode is reported. Charts on pp 11 - 13 are the most valuable part of the document.

PREDICTED PROPERTIES

Isotopes from the neutron dripline down to ²⁹¹Rf are predicted to decay primarily by beta emission, with half-lives increasing at A falls, reaching a peak of a few seconds near ²⁹¹Rf. Isotopes at the light end of this band are likely to decay by a mixture of beta emission and fission.

Between ²⁹⁰Rf and ²⁸¹Rf, beta decay is predicted to be the dominant mode. Ref 2 predicts long beta-decay half-lives between ²⁸⁸Rf and ²⁸³Rf, peaking at 20 d in ²⁸⁶Rf, and falling to around 30 sec at ²⁸¹Rf. A zone where beta decay half-lives rises, then falls as A declines seems anomalous. Ref. 3 predicts half-lives on the order of seconds down to and including ²⁸¹Rf. (Refs. 2 and 3, between them, indicate a half-life around 200 sec and decay primarily by beta emission, They indicate that ²⁸²Rf will have a strong fission branch.)

²⁸⁰Rf is predicted to decay by beta emission plus a 1% fission branch. Its half-life is predicted to be on the order of 300 sec.

Even-N isotopes between ²⁷⁸Rf and ²⁷⁰Rf are predicted to have millisecond-scale half-lives and to decay exclusively by fission. Odd-N isotopes down to ²⁷³Rf are predicted to have half-lives on the 1 sec scale, and to have a beta-decay branch. ²⁷¹Rf also has a second-scale half-life, but decays by alpha emission and fission, no beta decay.

Observation of ²⁷⁰Rf, ²⁶⁸Rf, and ²⁶⁶Rf has been reported, but not confirmed. Observation of ²⁶⁷Rf has been reported and confirmed⁽⁴⁾. Comparison of their observed decay properties with the predicted decay properties of these isotopes implies that predicted fission half-lives are to short by 1 to 1.5 orders of magnitude. ²⁶⁷Rf, which has a neutron count of 163, has an observed half-life up to 2.5 hr, probably making it the longest-lived Rf isotope. Few nuclei of ²⁶⁷Rf have been observed, and its half-life is uncertain. It may actually be on the order of 1.5 hrs.

Isotopes have been predicted or observed down to ²⁴¹Rf. Between ²⁴⁰Rf and ²³²Rf, there is a gap containing nuclides with half-lives in the 10^-14 - 10^-09 sec range or nuclear drops too short-lived to qualify as nuclides. Decay by fission is to be expected.

Ref. 3 predicts that a trio of isotopes, ²³¹Rf to ²²⁹Rf will have half-lives in the 10^-09 - 0.001 sec range. The lighter two are predicted to decay by alpha emission, the heaviest by fission. In addition, a second pair, ²²⁶Rf and ²²⁵Rf, are predicted to have half-lives exceeding 10^-09 sec and to decay by alpha emission.

OCCURRENCE

FORMATION

It appears likely that Rf isotopes from the neutron dripline down to ²⁷⁴Rf can form. In some cases, notably even-N isotopes ²⁸⁴Rf and lighter, fission branches in the decay chains leading to Rf will reduce the amount of Rf which forms, but do not completely cut off the beta-decay chains.

Ref 1 indicates that ²⁷³Lr decays entirely by fission, blocking the formation of ²⁷³Rf. This is uncertain. Beta-decay partial half-lives from Ref 2 and fission partial half-lives from Ref 2 indicate that a fission branch ratio on the order of 0.001 exists.

A beta-decay chain with A = 272 appears to be cut off at ²⁷²No 272. A chain with A = 271 is choked off by ²⁷¹No and ²⁷¹Lr in sequence.

Although the beta-decay chain leading to it heavily depleted by fission, it appears possible that some ²⁶⁹Rf may form.

²⁷⁰Rf, ²⁶⁸Rf, and lighter isotopes appear unlikely to form. Beta decay chains are interrupted by nuclides with no beta decay branch before reaching Rf. In addition, Lr reaches beta stability around ¹⁶⁷Lr 267, which means lighter chains cannot reach Rf.

Both large, neutron-rich nuclides ejected by disintegrating neutron stars and large nuclides produced by rapid neutron capture in both supernovae and neutron star mergers contribute to the production of all Rf isotopes which can form.

PERSISTENCE

Half-lives of Rf isotopes do not appear to exceed 3 hrs, nor do they have any long-lived precursors. In principle, some could persist for as much as a month after a supernova, neutron star merger, or other event which led to their formation.

ATOMIC PROPERTIES

Wikipedia's article "Rutherfordium" addresses the element's atomic properties and chemistry in some detail. It is unlikely that any Rf can survive, outside the laboratory, to reach an environment cool enough for chemical interactions to occur.

REFERENCES

1. "Chart of the Nuclides, 2014", Japan Atomic Energy Agency; website available using "chart of nuclides" and "JAEA" as internet search terms.

2. "Nuclear Properties for Astrophysical Applications"; P. Moller & J. R. Nix; Los Alamos National Laboratory website; search by "LANL, T2", then "Nuclear Properties for Astrophysical Applications".

3. "Decay Modes and a Limit of Existence of Nuclei"; H. Koura; 4th Int. Conf. on the Chemistry and Physics of Transactinide Elements; Sept. 2011.

4. "Isotopes of Rutherfordium", Wikipedia article.

5. Beta decay (electron or positron) is a weak-force interaction. The event itself is a quark flip, which takes around 10^-27 sec to occur. However, range of the weak force is so tiny that the right conditions rarely occur. The half-lives of beta-decaying nuclides bottom out around 0.001 sec.

9-Period Periodic Table of Elements
1	1 H																																																																	2 He
2	3 Li	4 Be																																																																	5 B	6 C	7 N	8 O	9 F	10 Ne
3	11 Na	12 Mg																																																																	13 Al	14 Si	15 P	16 S	17 Cl	18 Ar
4	19 K	20 Ca																																																																	21 Sc	22 Ti	23 V	24 Cr	25 Mn	26 Fe	27 Co	28 Ni	29 Cu	30 Zn	31 Ga	32 Ge	33 As	34 Se	35 Br	36 Kr
5	37 Rb	38 Sr																																																																	39 Y	40 Zr	41 Nb	42 Mo	43 Tc	44 Ru	45 Rh	46 Pd	47 Ag	48 Cd	49 In	50 Sn	51 Sb	52 Te	53 I	54 Xe
6	55 Cs	56 Ba																																																					57 La	58 Ce	59 Pr	60 Nd	61 Pm	62 Sm	63 Eu	64 Gd	65 Tb	66 Dy	67 Ho	68 Er	69 Tm	70 Yb	71 Lu	72 Hf	73 Ta	74 W	75 Re	76 Os	77 Ir	78 Pt	79 Au	80 Hg	81 Tl	82 Pb	83 Bi	84 Po	85 At	86 Rn
7	87 Fr	88 Ra																																																					89 Ac	90 Th	91 Pa	92 U	93 Np	94 Pu	95 Am	96 Cm	97 Bk	98 Cf	99 Es	100 Fm	101 Md	102 No	103 Lr	104 Rf	105 Db	106 Sg	107 Bh	108 Hs	109 Mt	110 Ds	111 Rg	112 Cn	113 Nh	114 Fl	115 Mc	116 Lv	117 Ts	118 Og
8	119 Uue	120 Ubn																															121 Ubu	122 Ubb	123 Ubt	124 Ubq	125 Ubp	126 Ubh	127 Ubs	128 Ubo	129 Ube	130 Utn	131 Utu	132 Utb	133 Utt	134 Utq	135 Utp	136 Uth	137 Uts	138 Uto	139 Ute	140 Uqn	141 Uqu	142 Uqb	143 Uqt	144 Uqq	145 Uqp	146 Uqh	147 Uqs	148 Uqo	149 Uqe	150 Upn	151 Upu	152 Upb	153 Upt	154 Upq	155 Upp	156 Uph	157 Ups	158 Upo	159 Upe	160 Uhn	161 Uhu	162 Uhb	163 Uht	164 Uhq	165 Uhp	166 Uhh	167 Uhs	168 Uho	169 Uhe	170 Usn	171 Usu	172 Usb
9	173 Ust	174 Usq
Alkali metal Alkaline earth metal Lanthanide Actinide Superactinide Transition metal Post-transition metal Metalloid Other nonmetal Halogen Noble gas predicted predicted predicted predicted predicted predicted predicted predicted predicted

(11-15-20)