Darmstadtium

Template:Infobox darmstadtiumDarmstadtium, Ds, is the name of element 110. Its appearance is a presumably metallic, silvery white, gray solid. Darmstadtium has been predicted to look like osmium. 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.

The longest lived Ds isotopes are expected in the band from ²⁹⁴Ds to ²⁸⁷Ds, with predicted half-lives ranging up to nearly 400 yr. With the exception of ²⁹⁴Ds, there appears to be agreement that all isotopes in this band can form. Some sources predict that ²⁹⁴Ds can form, others disagree. If ²⁹⁴Ds can form, it will persist for up to 50000 yr after an event which leads to its formation. Other isotopes in the band ²⁹³Ds to ²⁸⁷Ds are expect to persist for 5000, 16000, 600, 150, 3.6, and 35 years respectively. There are also numerous isotopes heavier than ³⁰¹Ds which can be expected to form, but disappear within 1000 sec.

Isotopes in the band ³⁰¹Ds to ²⁹⁵Ds cannot form because short-lived, fission-decaying nuclides interrupt beta-decay chains at Z < 110. Isotopes ²⁸⁶Ds and lighter cannot form because beta decay chains end at lower Z, either by reaching nuclides which either fission or emit alpha particles.

Ds is expected to be present in young supernova or kilonova (neutron star merger) remnants, although probably in quantities too small to detect. It is possible that Ds will interact chemically in such remnants, particularly with H, C, and O.

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. 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. 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 .

Japan Atomic Energy Agency (JAEA) maintains an on-line chart of nuclides which includes decay properties of many predicted nuclides - 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. 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 ³¹¹Ds are predicted to decay by beta emission and to have half-lives in the 0.001 - 1 sec range.

Between ³¹⁰Ds and ³⁰⁷Ds, predicts beta decay and half-lives greater than 0.001 sec, with most having predicted half-lives of a few seconds. Fission may be an important secondary decay mode in this band. predicts decay by fission with shorter half-lives, implying that beta decay does not occur.

Both sources predict decay by fission in the ³⁰⁶Ds to ³⁰³Ds band; but predicts long half-lives (> 0.001 sec) while predicts short half-lives (<10^-06 sec). If is accurate, beta decay is likely to be an important secondary decay mode. If is accurate, it is not.

and agree that decay by fission and short half-lives are the rule in the ³⁰⁰Ds to ²⁹⁸Ds band, Quantitatively, they disagree in how short half-lives are.

predicts that ²⁹⁷Ds and ²⁹⁶Ds decay by beta emission with half-lives of a few seconds. predicts fission and shorter half-lives.

Below ²⁹⁶Ds, there have been many studies of decay properties. There does seem to be consensus that fission will not be a significant decay mode, that half-lives will peak shortly below ²⁹⁵Ds, and that long half-lives will be possible near N = 184.

, , & all indicate ²⁹⁴Ds and ²⁹²Ds will decay primarily by alpha emission predicts half-lives of 380 yr & 130 yr respectively, while predicts 9500 yrs and 5300 yrs. Of these, is probably the more realistic. also predicts complete stability against beta decay, but branch ratios for decay by fission of 0.0004 and 0.04. is silent on this point, since it does not address fission. predicts decay by beta emission with a half-life of less than 1 day.

through predict that ²⁹⁵Ds and ²⁹³Ds will decay mainly by beta emission, although predicts longer half-lives than . It is likely that ²⁹⁵Ds has a half-life under 1 day, and that ²⁹³Ds has a half-life on the order of 40 yrs.

& predict that ²⁹¹Ds, while & predict stability against beta decay. predicts a half-life of 4 hrs, which is consistent with the 1 sec - 1 day range of .

, , & all predict that no Isotopes in the band ²⁹⁰Ds to ²⁸⁶Ds have a beta decay branch (either b- or b+). Except for ²⁸⁹Ds, concurs. This broad band of beta-stable nuclides is characteristic of even-Z elements. Beta decay below ²⁸⁶Ds will be (b+ / EC) decay.

The four references diverge in their predictions of decay properties in the ²⁹⁰Ds to ²⁸⁶Ds. predicts alpha decay exclusively; predicts fission exclusively (except for beta decay at ²⁸⁹Ds); and predicts alpha decay in ²⁹⁰Ds, ²⁸⁹Ds, and ²⁸⁷Ds; but fission in ²⁸⁸Ds and ²⁸⁶Ds. Because fission is likely to be more important for even-N isotopes, appears more reliable. As for half-lives, isn't useful because half-lives are likely to be too long, and doesn't take fission into account. predicts that all isotopes in the ²⁹⁰Ds to ²⁸⁶Ds band will have half-lives in the 1 - 86400 sec range. appears to be the most reliable. It predicts half-lives in this band, going downward from ²⁹⁰Ds, of 4.5 yr, 1.2yr, 10 days, 0.25 yr, and 23 hr.

There is general agreement among the sources used that, for ²⁸⁵Ds and lighter isotopes, that fission will become more important, and that (b+ / EC) decay will appear as a significant decay mode. There is also general agreement that half-lives will become shorter.

Further comparison of predicted decay properties or evaluation of likely actual properties is out of scope for this article.

Observed isotopes are found in a band from ²⁸¹Ds to ²⁶⁷Ds. Of the 8 odd-N isotopes in this band, only ²⁷⁵Ds has not been observed. predicts that its decay properties are not inconsistent with the observed isotopes. Four of the 7 even-N isotopes have never been observed. predicts very short fission half-lives for ²⁶⁴Ds, ²⁶⁶Ds, and ²⁶⁸Ds. With so few observed even-N observations, it is difficult to say whether these are inconsistent with observed decay properties. It should be noted, though, that a deformed shell closure has been predicted to occur at N = 162. Alpha decay half-lives are not predicted to drop greatly above ²⁷²Ds, but fission half-lives do. The predicted instability may be an anomaly, but may also reflect instability at N somewhat greater than 162.

The lightest isotope reported in the vicinity of N = 184 by any of 1 through 3 is ³⁶³Ds. There may be a few lighter nuclides with half-lives in the 10^-14 - 10^-09 sec range in this region, but half-lives will quickly decline below the minimum needed for a nuclear drop to qualify as a nuclide.

predicts that 3 isotopes in the band ²³⁹Ds to ²³⁶Ds will have half-lives in the 10^-09 - 10^-06 sec range. All are predicted to decay by proton emission. These isotopes have neutron counts from N = 126 to N = 129. They appear to be stabilized by the N = 126 neutron shell closure.

OCCURRENCE

FORMATION

Ds isotopes from the neutron dripline to ³⁰⁵Ds can form. Heavier isotopes in this band can form directly as a neutron star disintegrates; largely from dripline nuclides, but also as fission daughters of very large nuclear drops. Lighter isotopes require a chain of beta decays to form, but all lower-Z nuclides in such chains have long enough partial half-lives against fission that attrition will not be severe. The lightest isotopes are themselves short-lived, fission decaying species.

Below ³⁰⁵Ds, it is necessary to examine the possibility of fission attrition cutting off beta-decay chains below Z = 110. The article "Superheavy Island is Deserted" (this wiki) tabulates two sets of data for attenuation by fission and cutoff by nuclides which do not have a beta decay branch. Set 1 is based on & 3, and Set 2 is based on . Both sets indicate heavy fission attrition between ³⁰¹Ds and ²⁹⁴Ds; however, Set 1 predicts that only ²⁹⁸Ds and ²⁹⁶Ds will be completely cut off, Of particular interest, predicts that minute amounts of ²⁹⁴Ds can form. predicts that all isotopes between ³⁰⁰Ds and ²⁹⁴Ds will be completely cut off.

Both data sets predict that attrition by fission will not prevent the formation of isotopes in the band ²⁹³Ds to ²⁸⁷Ds.

and 4 predict that ²⁸⁶Hs & ²⁸⁴Hs have no beta-decay branches, which implies that ²⁸⁶Ds and ²⁸⁴Ds cannot form. predicts that ²⁸⁶Ds does beta-decay, but that ²⁸⁴Ds does not. It is uncertain whether ²⁸⁶Ds can form, but likely that ²⁸⁴Ds can.

and 4 both indicate a beta decay branch for ²⁸⁵Mt; but predicts a half-life exceeding 10⁰⁹ sec for that nuclide, which implies a small decay energy. What actually predicts is that ²⁸⁵Mt is almost stable. predicts complete beta stability, which is likely to be the case. It is unlikely that ²⁸⁵Ds can form, due to blocking at ²⁸⁵Mt.

For ²⁸³Ds and lighter isotopes, there appears to be general agreement that formation does not occur. predicts a beta-decay chain leading to the isotope, but also predicts that ²⁸³Ds itself decays by electron capture or positron emission, which would imply ²⁸³Ds <---> ²⁸³Mt, a physically questionable situation.

Material ejected from a disintegrating neutron star can be expected to contain nuclides with A covering the entire range of Rg isotopes which can form. Several studies of rapid neutron capture (r process) indicate that neutron capture reactions can produce nuclides with A up to around 380 before fission attrition prevents further growth. Supernovae contribute to production of most Rg isotopes, including all the long-lived ones.

PERSISTENCE

If ²⁹⁴Ds can form, it may persist for up to 50000 yr after a supernova, neutron star merger, or similar event leads to its formation. This is, by a wide margin, the longest-persisting Ds isotope. ²⁹²Ds is second, with a predicted persistence on the order of 16000 yrs, and is the longest-lived isotope for which there is general agreement that its formation is expected. Even though it beta-decays, ²⁹³Ds decays slowly (40 yr half-life), so it is predicted to persist for roughly 5000 yr. Four other isotopes, ²⁹⁰Ds to ²⁸⁷Ds are predicted to last for 600, 150, 3.6, and 35 years respectively. All other Ds isotopes are expected to persist for less than one year.

ATOMIC PROPERTIES

Wikipedia's article "Darmstadtium" addresses the element's atomic properties and chemistry in some detail. Although the amount of Ds which can form outside the laboratory is tiny, it does appear that Ds chemistry can exist without the presence of chemists.

REFERENCES

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

(10-16-20)