Dubnium

Dubnium, Db, is the name of element 105, 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.

Heavier isotopes, from the neutron dripline to ²⁸¹Db, plus odd-A isotopes down to ²⁷⁵Db can form. Maximum half-lives are reached in the lower 280s, and may be as great as 6 hrs. These isotopes may survive long enough to become part of supernova or kilonova (neutron star merger) remnants. They will disappear completely, though, within 2 - 3 months.

²⁶⁸Db has an observed half-life of roughly 30 hrs, which is much longer than other predicted or observed isotopes' half-lives. It cannot, however, form in quantity.

NUCLEAR PROPERTIES

INFORMATION SOURCES

This article uses two main resources chosen because of their independence from one another. A third source provides quantitative data over a limited range.

At least one document maps half-life and decay mode for elements below Z = 175 from the neutron dripline down to isotopes which are too neutron-poor to survive any appreciable length of time⁽¹⁾. Maps on pp 15 & 18 address the entire (Z,N) region covered, but report only the dominant decay mode and report half-lives only to within a band three orders of magnitude wide (0.001 - 1 sec, for example). More detailed estimates of these properties can be extracted from maps on pp 11 & 12, but only for a limited range of Z and N. Half-life data are reported by colors, which makes numerical estimates laborious to produce. This document is connected to Japan's KTUY model.

An independent map of half-lives and decay modes exists⁽²⁾. This one is limited to A = 339, as well as to Z = 132. It does not show short-lived isotopes well, and gives half-lives only within rather broad and awkward bands. It does show multiple decay modes for single nuclides. It originates from models used by the Russian agency JINR, so is completely independent of Ref. 1.

Japan Atomic Energy Agency (JAEA) maintains an on-line chart of nuclides which includes decay properties of many predicted nuclides⁽³⁾ - 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. These appear to be systematically too long, but are probably reliable to within an order of magnitude in most cases.

The U.S.'s Los Alamos National Laboratory (LANL) contains tabulated partial half-life data for alpha and beta decay⁽⁴⁾. If it included fission, it would be a primary resource for this article, but it does not. Where fission is not an issue, though, it constitutes a third independent source of decay properties.

PREDICTED PROPERTIES

Isotopes from the neutron dripline down to ²⁹³Db are predicted to decay primarily by beta emission, usually half-lives in the 0.001 - 1 sec range. Isotopes at the light end of this band are likely to decay by a mixture of beta emission and fission.

Between ²⁹²Db and ²⁸²Db, beta decay is predicted to be the dominant mode of decay. Half-lives are predicted to increase, to maxima on the order of 400 sec at ²⁸⁷Db and 600 sec at ²⁸⁶Db, then decline. This decrease is likely to reflect the increasing influence of fission.

²⁸¹Db is predicted to decay principally by fission and to have a half-life on the order of 1 hr.

²⁸⁰Db is predicted to decay by a mixture of beta emission and fission, and to have a half-life on the order of 6 hrs.

²⁷⁹Db is predicted to decay principally by fission and to have a half-life under 1000 sec.

²⁷⁸Db is predicted to decay by beta emission, with a half-life under 10 min.

Isotopes in the band ²⁷⁷Db to ²⁷²Db are predicted to decay principally by fission, with half-lives under 1 sec. Odd-N isotopes (odd-odd nuclei) are predicted to have weak beta-decay branches, while even-N isotopes are predicted to decay exclusively by fission. ²⁷¹Db is predicted to decay by fission, with an alpha decay branch, but no beta.The observed, long-lived, fission-decaying isotopes ²⁷⁰Db, ²⁶⁸Db, and ²⁶⁷Db influence the details of these predictions. Observed half-lives decline by a factor of 30 or so between ²⁶⁸Db and ²⁷⁰Db - then drop by a factor of 10000 to the predicted millisecond-scale half life predicted for ²⁷²Db. A similar gap exists between observed ²⁶⁷Db and predicted ²⁶⁹Db9. Both cases indicate that actual fission partial half-lives are likely to be greater than predicted. This will make beta-decay and alpha-decay branches stronger than predicted. (Note that N = 162 at ²⁶⁷Db).

Predictions for ²⁶⁵Db and ²⁶⁴Db are not inconsistent with the decline in half-lives and emergence of an important alpha-decay branch between ²⁶⁶Db and ²⁶³Db.

Ref 1 predicts a gap between ²⁴⁶Db and ²³⁴Db which contains either 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. 1 also predicts that a pair of isotopes, ²³³Db & ²³²Db will have half-lives in the 10^-09 - 10^-06 sec range. Both are predicted to decay by proton emission.

OCCURRENCE

FORMATION

It appears likely that Db isotopes from the neutron dripline to ²⁸³Db can form. Heavier isotopes can form directly, but the isotopes of greatest interest require a beta decay chain in order to form. Fission-decaying nuclides with Z < 105 with near A = 295 can be expected to reduce the quantity of material which reaches Db, but is not expected to completely block any decay chains.

It appears likely that odd-N isotopes between ²⁸¹Db and ²⁷⁵Db can form. ²⁸²Rf, ²⁸⁰Rf, ²⁷⁸Rf, and ²⁷⁶Rf do not have beta-decay branches, so that ²⁸²Db, ²⁸⁰Db, ²⁷⁸Db, and ²⁷⁶Db cannot form.

For ²⁷⁴Db and lighter, no Db isotopes can form. ²⁷³Db is blocked by ²⁷³Lr, for which no beta decay chain is reported. The others, down to ²⁷⁰Db, are blocked by short-lived, fission-decaying Rf isotopes.

²⁷⁰Db and lighter isotopes are unlikely to form,

Both large, very neutron rich nuclides expelled by disintegrating neutron stars and large nuclides produced by rapid neutron capture can contribute to all Db isotopes which can form. Both supernovae and neutron star mergers can produce Db.

PERSISTENCE

Half-lives of isotopes in the ²⁹³Db to ²⁸¹Db may be as much as 6 hrs. In principle, some could persist for as much as two months after a supernova, neutron star merger, or other event which led to their formation. Other isotopes are expected to persist for shorter times. They are present in detectable amounts for a much shorter time,

The observed isotope ²⁶⁸Db has a half-life around 30 hrs. However, since it cannot form, there is no point in asking how long it persists.

ATOMIC PROPERTIES

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

REFERENCES

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

2. “Systematic Study of Decay Properties of Heaviest Elements.”; Y. M. Palenzuela, L. F. Ruiza, A. Karpov, and W. Greiner; Bulletin of the Russian Academy of Sciences, Physics.  Vol . 76, No.11, pp 1165 – 1177; 2012

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

4. "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".

5. "Isotopes of Dubnium", Wikipedia article.

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

(11-10-20)