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Alpha lifetime of lead?

  1. Nov 13, 2014 #1
    What is supposed to be the lifetime of lead against alpha decay?

    Notable light isotopes that DO undergo alpha decay:
    Be-8 188 keV 7*10ˇ-16 s
    Sm-146 2529 keV 103*10ˇ6 y
    U-235 4679 keV 704*10ˇ6 y
    U-238 4270 keV 4,47*10ˇ9 y
    Th-232 4083 keV 14,06*10ˇ9 y
    Sm-147 2310 keV 106,1*10ˇ9 y
    Pt-190 3252 keV 650*10ˇ9 y
    Gd-152 2203 keV 110*10ˇ12 y
    Hf-174 2497 keV 2*10ˇ15 y
    Os-186 2823 keV 2*10ˇ15 y
    Nd-144 1905 keV 2,3*10ˇ15 y
    Sm-148 1986 keV 7*10ˇ15 y
    W-180 2509 keV 1,8*10ˇ18 y
    Eu-151 1964 keV 5*10ˇ18 y
    Bi-209 3137 keV 19*10ˇ18 y

    Now isotopes which might release rest mass energy by alpha decay, but do NOT:
    Os-184 2963 keV
    Os-187 2720 keV
    Pt-192 2418 keV
    Hf-176 2255 keV
    Hf-177 2245 keV
    Re-185 2195 keV
    Os-188 2143 keV
    Ta-180 2103 keV
    Ir-191 2084 keV
    Hf-178 2083 keV
    Hg-196 2027 keV
    Os-189 1976 keV
    Pb-204 1972 keV
    Yb-168 1951 keV
    Sm-149 1870 keV
    Hf-179 1806 keV
    W-182 1772 keV
    Dy-156 1758 keV
    Yb-170 1738 keV
    W-183 1680 keV
    W-186 1656 keV
    Er-162 1646 keV
    Lu-175 1620 keV
    Nd-145 1578 keV
    Yb-171 1559 keV
    Ta-181 1526 keV
    Pt-194 1504 keV
    Sm-150 1449 keV
    Hg-198 1383 keV
    Os-190 1378 keV
    Yb-172 1310 keV
    Er-164 1304 keV
    Ce-142 1298 keV
    Hf-180 1283 keV
    Tm-169 1200 keV
    Nd-146 1182 keV
    Pt-195 1158 keV
    Pb-206 1137 keV
    W-186 1123 keV
    Ir-193 1017 keV
    Au-197 954 keV
    Yb-173 946 keV
    Tl-203 911 keV
    Dy-158 875 keV
    Er-166 831 keV
    Hg-199 824 keV
    Pt-196 794 keV
    Yb-174 740 keV
    Hg-200 718 keV
    Er-167 666 keV
    Nd-148 599 keV
    Yb-176 570 keV
    Er-168 553 keV
    Nd-143 521 keV
    Pb-208 519 keV
    Dy-160 439 keV
    Pb-207 391 keV
    Os-192 362 keV
    Dy-161 344 keV
    Hg-201 334 keV
    Eu-153 274 keV
    Sm-152 220 keV
    Tl-205 157 keV
    Ho-165 139 keV
    Hg-202 136 keV
    Pt-198 87 keV
    Dy-162 85 keV
    Gd-155 81 keV
    Gd-154 81 keV
    Sm-144 76 keV
    Er-170 50 keV

    So, what are the estimates for the half-lives of the above isotopes not known to decay?
     
  2. jcsd
  3. Nov 13, 2014 #2

    mathman

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    http://atom.kaeri.re.kr/ton/
    Above contains the information you are looking for.

    I looked at the Os isotopes. 184 has extremely long half life. Os-187 is stable.
     
  4. Nov 13, 2014 #3

    Simon Bridge

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    If the isotope is not known to decay, then it's half-life is estimated as "infinite". That is what "stable" means
    Pb208, for instance, is the heaviest known stable nucleus.

    You can look up decay rates in tables of isotopes - which you can find in a college library or a teaching lab than includes radioactivity experiments. There are quite a few online too:
    i.e. http://ie.lbl.gov/toi/nuclide.asp?iZA=820210 (Pb210)
    http://atom.kaeri.re.kr/ton/

    Wikipedia has the usual graphic showing the distribution of different decay modes.
     
  5. Nov 13, 2014 #4

    Astronuc

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    U-235 4679 keV 704*10ˇ6 y
    U-238 4270 keV 4,47*10ˇ9 y
    Th-232 4083 keV 14,06*10ˇ9 y
    Bi-209 3137 keV 19*10ˇ18 y

    are not considered light isotopes. They are considered heavy, and certainly heaviest of the naturally occurring isotopes, except for Bi- which is not as heavy as the U-isotopes.
     
  6. Nov 14, 2014 #5
    Look further.
    That 56*10ˇ12 years is lower bound! No upper bound, therefore no decay.

    How come that a natural isotope with no upper bound of half-life has a lower bound as short as 56*10ˇ12 years, seeing that bismuth has upper bound of alpha decay lifetime at 19*10ˇ18 years, and even longer upper bounds are observed for some double beta decays?

    Also, for the isotopes that do have observed long lifetimes, how well do the observed values fit theoretical predictions?
    Now, most of these known long-lived isotopes:
    Pt-190 3252 keV 650*10ˇ9 y
    Gd-152 2203 keV 110*10ˇ12 y
    Hf-174 2497 keV 2*10ˇ15 y
    Os-186 2823 keV 2*10ˇ15 y
    Nd-144 1905 keV 2,3*10ˇ15 y
    Sm-148 1986 keV 7*10ˇ15 y
    W-180 2509 keV 1,8*10ˇ18 y
    are even-even. Easy. Mother even-even, ground state spin zero, alpha even-even ground state spin zero, daughter even-even ground state spin zero. No complications.
    But how about
    Eu-151 1964 keV 5*10ˇ18 y 5/2+ daughter Pm-147 7/2+ and beta lifetime 2,6 y
    Bi-209 3137 keV 19*10ˇ18 y 9/2- daughter Tl-205 1/2+
    Do their lifetimes match forecasts?
     
  7. Nov 14, 2014 #6

    mfb

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    Different experimental challenges (like: how clean do you get your sample, especially if other natural isotopes of the element are radioactive) and different interest in the various isotopes.
    Beta decay is way easier to measure as you get an electron out. Or even two in coincidence in case of double beta decay.
     
  8. Nov 22, 2014 #7

    arivero

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    You should clarify if you are asking for lower bounds or for theoretical estimates. I'd like to hear about the second.
     
  9. Nov 24, 2014 #8
    So would I. I wouldn´t expect experimental lower bounds to be significant for lead.
    Tried looking at it another way: the minimum alpha decay energy of isotopes by element.
    59 - Pr - no alpha decay
    60 - Nd - 4 isotopes can release energy by alpha decay, but not 142-Nd
    61 - Pm - all isotopes unstable to single beta
    62 - Sm - 76 keV of Sm-144, which also is able to double electron capture. Of double beta stable isotopes, 220 keV Sm-152
    63 - Eu - 274 keV Eu-153
    64 - Gd - 3 isotopes stable to alpha
    65 - Tb - stable to alpha
    66 - Dy - 2 isotopes stable to alpha. Dy-164 is the heaviest nucleus which qualifies to that and also is stable to double beta.
    67 - Ho - 139 keV Ho-165

    68 - Er - 50 keV of Er-170, which also is able to double beta decay. Of double beta stable isotopes, 553 keV Er-168
    69 - Tm - 1200 keV Tm-169
    70 - Yb - 570 kev Yb-176, also able to double beta decay. Of double beta stable isotopes, 740 keV Yb-174
    71 - Lu - 1620 keV Lu-175
    72 - Hf - 1283 keV Hf-180
    73 - Ta - 1526 keV Ta-181
    74 - W - 1123 keV W-186
    75 - Re - 2195 keV Re-185
    76 - Os - 362 keV Os-192, also able to double beta decay. Of double beta stable isotopes, 1378 keV Os-190
    77 - Ir - 1017 keV Ir-193
    78 - Pt - 87 keV Pt-198, also able to double beta decay. Of double beta stable isotopes, 794 keV Pt-196
    79 - Au - 954 keV Au-197
    80 - Hg - alpha stable Hg-204 (the only such heavier than Dy-164) able to double beta decay. Of double beta stable isotopes, 136 keV Hg-202
    81 - Tl - 157 keV Tl-205
    82 - Pb - 391 keV Pb-391

    83 - Bi - 3137 keV Bi-209

    Looks like the bolded elements Hg to Pb form a stability island! All isotopes of all elements from 71 Lu to 75 Re release at least 1 MeV on alpha decay.
     
  10. Nov 24, 2014 #9

    arivero

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    Thinking aloud, I'd say that the theory should compose a probability of extracting two protons from the proton shell plus two neutrons from the neutron shell (the shells are nearby, of course, because of beta decay) and then the probability of crossing the barrier. This second prob should depend of Z and the total energy, while the former should depend of shell structure and thus both of Z,N.
     
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