HeII Case B Recombination Coefficients

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Alpha B HeII.png

Recombination coefficients for HeII -> HeI, Case B.

Contents

BS60

Burgess & Seaton 1960 MNRAS 121, 471

My fit to BS60's 2 data points:

\alpha_{A HeII} = 5.28\times 10^{-16} T^{-0.8219} \mathrm{m}^{3} \mathrm{s}^{-1}

AAM (VF96 - α1)

Verner & Ferland 1996, ApJS 103, 467

\alpha^A_{HeII} = a \left[ (T/T_0)^{1/2} (1+(T/T_0)^{1/2})^{1-b} (1+(T/T_1)^{1/2})^{1+b}\right]^{-1} - 0.4 a T^{-0.48}

a=3.294\times 10^{-17}\mathrm{m}^3 \mathrm{s}^{-1}
b = 0.6910
T0 = 15.54K
T_1=3.676\times 10^7 \mathrm{K}

HG97

Hui & Gnedin 1997 MNRAS 292, 27

Their fit to BS60's 2 data points:

\alpha_{A HeII} = 5.28\times 10^{-16} T^{-0.8219} \mathrm{m}^{3} \mathrm{s}^{-1}

5\times 10^3 \mathrm{K} < T < 5\times 10^5 \mathrm{K}

ET: Fit to HS98

\alpha_\mathrm{A HeII} = 1.007\times 10^{-16} T^{-0.5095} e^{-0.01429 \ln(T)^2}

HS98

Hummer & Storey 1998, MNRAS 297, 1073

log(T) αB[10 − 17m3s − 1 ]
1.0 9.284
1.2 8.847
1.4 8.403
1.6 7.952
1.8 7.499
2.0 7.044
2.2 6.589
2.4 6.136
2.6 5.685
2.8 5.238
3.0 4.797
3.2 4.364
3.4 3.940
3.6 3.528
3.8 3.132
4.0 2.755
4.2 2.401
4.4 2.073

See Also

Recombination Coefficients

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