Chmisry 988 Par 1 Radiaion Dcion & Masurmn Dp. of Chmisry --- Michigan Sa Univ. aional Suprconducing Cycloron Lab DJMorrissy Spring/2oo9 Cours informaion can b found on h wbsi: hp://www.chmisry.msu.du/courss/cm988uclar/indx.hml
Chap. 1 Radiaion Sourcs.. Wha? Ionizing Radiaion: a ypical Ionizaion Ponial for a molcul (or work funcion for a mal) is a fw V.. Thus, w will b concrnd wih sourcs ha produc radiaions wih significanly mor nrgy han his (lar w will s ha h imporan paramr for dcors is an ffciv ionizaion ponial somwha largr han h minimum). Radiaion yps: sor by mass & charg Gamma rays Elcrons +/- urons uclar Chargd Paricls Rquird Informaion: nuclid (, radiaions), amoun ( 0 ) d d d d 1 0 1 0 2 0 1, manlif ln2 T 12, half lif uxiliary informaion: puriy Spcificciviy mass MM Spcificciviy mass (if pur) MM ( ) (if pur)
Radiaion Sourcs.. Growh Sourcs: wih a vry fw xcpions h radioaciv sourcs ha w us hav o b producd in nuclar racions. Th producion can b dirc such as in a nuron capur procss (n,γ) or indircly by h dcay of anohr nuclid. Growh: a nuclar racion of h sor x +, whr will b our sourc marial d d d d ( ProducionRa) ( DcayRa) 0 σ x Φ x Limi: If is sabl, 0 0 x x 1 1 2 ( σ Φ )( 1 ) 0 x x Producion up o 1, subsqun dcay 2 1
τ τ < >τ τ τ τ >> τ τ >> >> τ τ Radiaion Sourcs.. Growh & Dcay Growh & Dcay: ofn a sourc may consis of a dcay chain: C ( ) ( ) ( ) bu d d d d + 0 0 0 ) (... ) ( ) ( ) ( Dcay Ra Producion Ra Som xampls for various cass of τ viz. τ.. h curvs ar h aciviis.
Radiaion Sourcs.. Elcrons 1 a Dcay: n p + + - + ν + Q.g., 14 C 14 + + - + ν + Q Q M( 14 0 ) - M( 14 C) and (p + n + + + ν + Q ).g., 13 13 C - + + + ν + Q 13 13 C 0 + - + + + ν + Q Thr-bodis in final sa givs coninuous nrgy disribuion bu hr ar housands of radioaciviis o choos from. o limis: 0 < Kinic Enrgy < Q Q M( 13 C 0 ) + 2 m o c 2 -M( 14 C) Phas spac or Frmi Funcions hav Coulomb shifs 64 Cu 64 i - + + + ν + Q β+ 0.6529 MV 64 Cu 64 Zn + + - + ν + Q β 0.5782 MV lso lcron capur: 64 Cu 64 i + ν + Q β+ 1.675 MV Typical nrgy scal
Radiaion Sourcs.. Elcrons 2 Inrnal convrsion: Z* Z + + -, whr h lcron was a bound aomic lcron. 207 i (38 yr) 207 Pb * + ν + Q c Two-bodis in final sa givs a discr nrgy disribuion of lcrons bu hr ar rlaivly fw xampls of sourcs (compard o ba-dcay). 207 Pb + + - (KEΔE aomic.e. ) K: 88 kv, L: 16 kv (n1, 1s) (n2, 2s,2p) Typical nrgy scal 9/2-207 i 7% 83% 10% 7/2-2.3399 MV M1 ΔE 1.4422 13/2+ 1.6333 MV, 0.81 s M4 ΔE 1.064 5/2-0.5696 MV, 131 ps E2 ΔE 0.5696 207 Pb 1/2- g.s.
Radiaion Sourcs.. Chargd Paricls 1 lpha Dcay: Z -4 (Z-2) 2- + 4 H 2+ +Q α.g., 238 U 234 Th 2- + 4 H 2+ + Q α Q α M[ -4 (Z-2) 0 ] +M[ 4 H 0 ] M[ Z] ucli havir han ~ 150 ar hrmodynamically unsabl agains alpha dcay bu bcaus h nrgy of dcay is much lowr han h Coulomb barrir i is a quanum mchanical unnling procss ha is xrmly snsiiv o h Q-valu of h procss. Thus, alpha dcay is only imporan for h havis nucli and i rarly fds xcid sas. Th paricls ar qui nrgic 4-9 MV bu inrac vry fficinly wih lcrons in marials and sop wihin ~100 microns in solids. Two-body final sa givs a discr nrgy disribuion mus accoun for rcoil nrgy. E.g., h 4n naural dcay chain: 232 228 228 Th 10 Ra c α,10 yr β β 228 Th 228 Th α,1.9 yr 224 Ra α,4d 220 Rn α,56s 216 Po α,0.2s 212 Pb 212 Pb β,11hr 212 i β,61m α E α 6.05, 6.09 MV 212 208 Po Tl α,0.3μs β,3 m 208 208 Pb Pb* E α 8.78 MV E γ 2.61 MV
Radiaion Sourcs.. Chargd Paricls 2 Sponanous Fission: Z -x (Z-y)* + x y* + Q f.g., 252 Cf (~3% SF) TKE 185 MV Sponanous fission is anohr quanum mchanical unnling procss similar o alpha-dcay ha is rar in h ligh acinid nucli and incrass in imporanc wih Z and limis h sabiliy of nucli wih Z>98. ll fission procsss produc a saisical disribuion of radioaciv producs, fas nurons and γ s. Two-body final sa givs a discr nrgy disribuion for ach fission vn bu hr ar many mass-splis and nuron vaporaion from h xcid fragmns. Ths fragmns go on o β- dcay vnually raching sabiliy. From: Schmi & Plasonon, IM 40 (1966) 204
Radiaion Sourcs.. γ rays Gamma rays ar mid by nuclar xcid sas, hir lifims ar gnrally oo shor o provid usful sourcs (xcp for som spcial cass calld isomric sas). a-dlayd: (Z+/-1) Z* Z + γ h gamma dcay is for many purposs promp, bu ofn h lifims of h xcid sas ar significan and hir xponnial dcay can b masurd. Two-bodis in final sa givs a 5+ 5.27 yr discr nrgy disribuion 60 Co 100% β- E2 ΔE 1.173 E2 ΔE 1.3325 60 i 4+ 2.506 MV, 1.1ps 2+ 1.3325 MV, 0.71 ps 0+ g.s. Thr will b an angular corrlaion among h ba and wo gammas.. nnihilaion: 1/2-13 C 100% β+ 1/2-9.965m 13 rmssrahlung: from lcron bams, coninuous nrgy spcrum primarily usd for irradiaions
Radiaion Sourcs.. nurons urons hav o b producd in nuclar racions, h nrgy spcrum will dpnd on h racion.. Sponanous Fission: 252 Cf h nurons ar primarily mid wih a hrmal nrgy spcrum in h rs fram of h moving fragmns (KE ~ 1 MV/u). Pu & m: inimaly mixd mals Phoonuclar Racions: I E 1/ 2 E / T 238 Pu 234 U 2- + 4 H 2+ + Q α 5.7012 MV, KE α < 5.14 MV 4 H 2+ + 9 13 C 2+ * 12 C 2+ + n + Q gg MV 12 C 2+ * + n + Q γ + 9 8 + n + Q gg -1.666 MV 124 Sb 124 T* (firs xcid sa) 124 T + γ 1.691 MV, n Q n 0.025 MV cclraor Racions: p+ 7 Li 7 + n + Q gg -1.64 MV d + 9 10 + n + Q gg +4.36 MV [MdCyc] d + d n + 3 H + Q gg +3.26 MV d + n + 4 H + Q gg +17.6 MV [fusion racion]