Calculation of atomic radiations in nuclear decay BrIccEmis and beyond

Transcription

1 Calculation of atomic radiations in nuclear decay BrIccEmis and beyond T. ibèdi, B.Q. Lee, A.E. Stuchbery,.A. Robinson in collaboration with F.G. ondev (ANL) Tibor ibèdi, Dep. of Nuclear Physics, Australian National University DDEP Workshop, Paris, 8-10 October 2012

2 Outline Talk is largely based on ȧlmȧn Robertson (ANU) Honours project (2010) Boon Quan Lee (ANU) Honours project (2012) 2012Le09 Lee et al., Atomic Radiations in the Decay of Medical Radioisotopes: A Physics Perspective Computational and Mathematical Methods in Medicine Volume 2012, Article ID , doi: /2012/ NSDD meeting (IAEA) Radiative and Non-radiative atomic transitions in nuclear decay Nuclear and atomic data Existing programs to evaluate atomic radiations New model based on Monte Carlo approach Future directions

3 Atomic radiations - Basic concept 3D 3P 3S 2P 2S M 5 M 4 M 3 M 2 M 1 L 3 L 2 L 1 Vacancies on the inner-shell can be produced by electron impact photo ionization ion-atom collision internal conversion electron capture secondary processes accompanying b-decay or electron capture 1S Initial vacancy

4 Atomic radiations - Basic concept X-ray emission 3D 3P 3S M 5 M 4 M 3 M 2 M 1 2P 2S L 3 L 2 L 1 1S EX a 2 L2 a2 X-ray 1 secondary vacancy Initial vacancy Tibor ibèdi, Dep. of Nuclear Physics, Australian National University DDEP Workshop, Paris, 8-10 October 2012

5 Atomic radiations - Basic concept X-ray emission 3D 3P 3S M 5 M 4 M 3 M 2 M 1 M 5 M 4 M 3 M 2 M 1 2P 2S L 3 L 2 L 1 L 3 L 2 L 1 1S EX a 2 L2 a2 X-ray 1 secondary vacancy Initial vacancy Tibor ibèdi, Dep. of Nuclear Physics, Australian National University DDEP Workshop, Paris, 8-10 October 2012 Initial vacancy

6 Atomic radiations - Basic concept X-ray emission Auger-electron 3D 3P 3S M 5 M 4 M 3 M 2 M 1 M 5 M 4 M 3 M 2 M 1 2P 2S L 3 L 2 L 1 L 3 L 2 L 1 1S EX a 2 L2 a2 X-ray 1 secondary vacancy Initial vacancy Tibor ibèdi, Dep. of Nuclear Physics, Australian National University DDEP Workshop, Paris, 8-10 October 2012 E L2L3 L2 Initial vacancy L2 L3 L2 L3 Auger-electron 2 new secondary vacancies

7 Atomic radiations - Basic concept X-ray emission Coster-ronig electron 3D 3P 3S M 5 M 4 M 3 M 2 M 1 M 5 M 4 M 3 M 2 M 1 2P 2S L 3 L 2 L 1 L 3 L 2 L 1 Initial vacancy 1S EX a 2 L2 a2 X-ray 1 secondary vacancy Initial vacancy Tibor ibèdi, Dep. of Nuclear Physics, Australian National University DDEP Workshop, Paris, 8-10 October 2012 E L1L2M1 L1 L2 L2 M1 L1 L2 M1 Coster-ronig transition 2 new secondary vacancies

8 Atomic relaxation and vacancy transfer A vacancy cascade in Xe From M.O. rause, J. Phys. Colloques, 32 (1971) C4-67 O 1,2,3 N 4,5 N 2,3 N 1 M 4,5 M 3 M 2 M 1 L 3 L 2 L 1 A A A C A A A A A A A A A A Full relaxation of an initial inner shell vacancy creates vacancy cascade involving X-ray (Radiative) and Auger as well as Coster-ronig (Non-Radiative) transitions Many possible cascades for a single initial vacancy Typical relaxation time ~10-15 seconds Many vacancy cascades following a single ionisation event! X Initial vacancy

9 Transition energies and Rates For a single initial vacancy on the -shell following nuclear decay Number of primary vacancies Internal conversion n P a 1 a T Electron capture n P P X-ray emission Auger-electron Energy EX Y E Y E XY E X X Y in an ion Intensity I Y X n I XY n a a 1 for L1 shell I X n L1Y L 1 L1 I n ( a f f 3) L1XY L1 L1L2 L1L L1 al 1 fl 1L2 fl 1L3 1

10 Medical applications - Auger electrons Biological effect: Linear energy transfer LET, kev/mm electrons assis, Int. J. of Radiation Biology, 80 (2004) 789

11 Medical applications - Auger electrons 2011 August, INDC International Nuclear Data Committee Technical Meeting on Intermediate-term Nuclear Data Needs for Medical Applications: Cross Sections and Decay Data Edited by A.L. Nichols, et al., Targeted tumor therapy NDC(NDS)-0596 Auger emitters: 67 Ga, 71 Ge, 77 Br, 99m Tc, 103 Pd, 111 In, 123 I, 125 I, 140 Nd, 178 Ta, 193 Pt, 195m Pt, 197 Hg Regaud and Lacassagne (1927) The ideal agent for cancer therapy would consist of heavy elements capable of emitting radiations of molecular dimensions, which could be administered to the organism and selectively fixed in the protoplasm of cells one seeks to destroy. (Courtesy of Thomas Tunningley, ANU).

12 Existing calculations Physical approach Nuclear decay data Conversion coefficients Electron Capture Ratios RADAR DDEP Eckerman & Endo (2007) Howell (1992) Stepanek (2000) Pomplun (2012) ENSDF DDEP ENSDF ENSDF ENSDF ICRP38 HsIcc RpIcc/BrIcc RpIcc, 1978 Band 1971 Gove & Martin 1995 Schönfeld 1977 Bambynek 1971 Gove & Martin, 1970Martin RpIcc 2000 Stepanek HsIcc, 1971 Dragoun, 1976 Band 1971 Gove & Martin, 1970Martin 1971 Gove & Martin Atomic transition rates 1972 Bambynek, RADLST 1974 Scofield, 1995 Schönfeld & Janßen, 2006 Be et al., EMISSION 1991 Perkins, EDISTR Chen, 1972/1975 McGuire, 1983 assis, 1974 Scofield, 1974 Manson & enedy 1991 Perkins 1979 Chen, 1972/1975 McGuire, 1970 Storm & Israel, 1979 rause Atomic transition energies 1970 Bearden & Burr, Neutral atom 1977 Larkins, Semi-empirical 1991 Perkins, Neutral atom Z/Z+1 (Auger), Neutral atom (Xray) Dirack-Fock calculation 1991 Desclaux, Dirack-Fock calculation Vacancy propagation Deterministic Deterministic Deterministic (+++) Monte Carlo with charge neutralization Monte Carlo Monte Carlo

13 Existing calculations Auger electron yield per nuclear decay RADAR DDEP Eckerman & Endo (2007) Howell (1992) Stepanek (2000) Pomplun (2012) 99m Tc (6.007 h) In (2.805 d) I (13.22 h) I (59.4 d) Tl (3.04 d) Vacancy propagation Deterministic Deterministic Deterministic (+++) Monte Carlo with charge neutralization Monte Carlo Monte Carlo

14 Existing programs Common problems / limitations In some cases neutral atom binding energies are used for atoms with vacancies; i.e. for ions Single initial vacancy is considered. Secondary vacancies are ignored Atomic radiations only from primary vacancies on the and L shell Limited information on sub-shell rates Auger electrons below ~1 kev are often omitted

15 BrIccEmis Monte Carlo approach for vacancy creation and propagation Initial state: neutral isolated atom Nuclear structure data from ENSDF lectron capture (EC) rates: Schönfeld (1998Sc28) Internal conversion (IC) coefficients: BrIcc (2008i07) Auger and X-ray transition rates: EADL (1991 Perkins) Calculated for single vacancies! Auger and X-ray transition energies: RAINE (2002Ba85) Calculated for actual electronic configuration! Vacancy creation and relaxation from EC and IC are treated independently Ab initio treatment of the vacancy propagation: Transition energies and rates evaluated on the spot Propagation terminated once the vacancy reached the valence shell

16 BrIccEmis Reads the ENSDF file, evaluates absolute decay intensities of EC, GAMMA, CE and PAIR transitions Simulates a number (100k-10M) radioactive decays followed by atomic relaxation lectron configurations and binding energies stored in memory (and saved on disk). New configurations only calculated if needed. ( 55 Fe: 15 k, 201 Tl: 1300k) mitted atomic radiations together with shells involved stored like histories in large files (several Gb) Separate files for X-rays and Auger electrons Smaller programs to sort/project energy spectra, produce detailed reports

17 111 In EC vacancy propagation Tibor ibèdi, Dep. of Nuclear Physics, Australian National University DDEP Workshop, Paris, 8-10 October 2012

18 99m Tc atomic radiations kev below L-shell BE

19 99m Tc atomic radiations X-rays DDEP a E-2 a E-2 b E-2 L [2.134:3.002] 4.82E-3 BrIccEmis E E E E-3 M E-4 N E-1

20 99m Tc atomic radiations Auger electrons DDEP BrIccEmis LL [14.86:15.58] 1.49E-2 LX [17.43:18.33] 2.79E-3 XY [19.93:21.00] 2.8E-4 -total C LLM 2.15E E E E E E C LLX E-3 LMM E-2 LMX E-2 LXY E-4 L-total [1.6:2.9] 1.089E E-1 Tibor ibèdi, Dep. of Nuclear Physics, Australian National University DDEP Workshop, Paris, 8-10 October 2012

21 99m Tc atomic radiations Auger electrons DDEP BrIccEmis C MMX E-1 MXY E+0 Super C NNN E-1 C NNX E-1 Total yield Auger electron per nuclear decay

22 99m Tc Auger electrons BrIccEmis: spectrum from 10 M simulated decay events No experimental spectrum to compare with

23 111 In experiment vs calculation E.A. Yakushev, et al., Applied Radiation and Isotopes 62 (2005) 451 ESCA; FWHM = 4 ev Calculations normalized to the strongest experimental line

24 111 In experiment vs calculation ESCA; FWHM = 7 ev Calculated energies are higher L 2 L 3 ( 1 D 2 ) energy (ev): A. ovalik, et al., J. of Electron Spect. and Rel. Phen. 105 (1999) (14) Experiment ovalik (1999) Semi-empirical Larkins (1979La19) RAINE (2002Ba85) Multiplet splitting could not be reproduced in JJ coupling scheme Similar discrepancies have been seen in other elements (Z=47, awakami, Phys. Lett A121 (1987) 414)

25 -shell binding energies for superheavy elements (2012i04) 2002Ga47 & 2008Th05: Breit magnetic electron interaction and the quantum electrodynamical (QED) corrections.

26 Breit and other QED contributions (2002Ga47) Z=49 (In) ~60 ev Alternative solution: Semi empirical corrections, like Larkins (1977La19) or Carlson (1977Ca31) used

27 Only a handful of measurements exist for ionization by nuclear decay 131m Xe: F. Pleasonton, A.H. Snell, Proc. Royal Soc. (London) 241 (1957) Ar: A.H. Snell, F. Pleasonton, Phys. Rev. 100 (1955) 1396 Good tool to asses the completeness of the vacancy propagation BrIccEmis: mean value is lower by ~ charge 131m Xe IT charge state at the end of atomic relaxation

28 Summary RelaxData/BrIccRelax BrIccEmis: calculation intensive approach (hours to days) RelaxData (under development): Nuclear decay event (EC or CE) produces a SINGLE INITIAL vacancy Considering a single atomic vacancy the relaxation process independent what produced the vacancy Compile a database of atomic radiation spectra for produced by a single initial vacancy on an atomic shell Carry out calculations of all elements and shells Example: 55 Fe EC, 7 shells for Z=25 and 26, calculated in couple of hours (1 M each shell) Replace EADL fixed rates and binding energies from RAINE with GRASP2k/RATIP calculations BrIccRelax (under development): Evaluate primary vacancy distribution and construct atomic spectra from the data base (20 seconds for 55 Fe EC)