Bound coherent scattering length · natural isotopic abundance
The neutron sees a different periodic table
Each disc has a radius proportional to the scattering length, so its area is the coherent cross section. Blue scatters in phase; rust means b < 0, a π phase shift on reflection. Switch to X-rays to watch the erratic pattern collapse into a smooth ramp with Z.
NEUTRON b
X-RAY f(0)
radius ∝ |b|, max = Dy 16.9 fm
1 H -3.74 2 He +3.26 3 Li -1.90 4 Be +7.79 5 B +5.30 6 C +6.65 7 N +9.36 8 O +5.80 9 F +5.65 10 Ne +4.57 11 Na +3.63 12 Mg +5.38 13 Al +3.45 14 Si +4.15 15 P +5.13 16 S +2.85 17 Cl +9.58 18 Ar +1.91 19 K +3.67 20 Ca +4.70 21 Sc +12.29 22 Ti -3.44 23 V -0.38 24 Cr +3.63 25 Mn -3.75 26 Fe +9.45 27 Co +2.49 28 Ni +10.30 29 Cu +7.72 30 Zn +5.68 31 Ga +7.29 32 Ge +8.19 33 As +6.58 34 Se +7.97 35 Br +6.79 36 Kr +7.81 37 Rb +7.09 38 Sr +7.02 39 Y +7.75 40 Zr +7.16 41 Nb +7.05 42 Mo +6.71 43 Tc +6.80 44 Ru +7.03 45 Rh +5.88 46 Pd +5.91 47 Ag +5.92 48 Cd +4.87 49 In +4.07 50 Sn +6.22 51 Sb +5.57 52 Te +5.80 53 I +5.28 54 Xe +4.92 55 Cs +5.42 56 Ba +5.07 72 Hf +7.70 73 Ta +6.91 74 W +4.86 75 Re +9.20 76 Os +10.70 77 Ir +10.60 78 Pt +9.60 79 Au +7.63 80 Hg +12.69 81 Tl +8.78 82 Pb +9.40 83 Bi +8.53 84 Po 85 At 86 Rn 87 Fr 88 Ra +10.00 104 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 57 La +8.24 58 Ce +4.84 59 Pr +4.58 60 Nd +7.69 61 Pm +12.60 62 Sm +0.80 63 Eu +7.22 64 Gd +6.50 65 Tb +7.38 66 Dy +16.90 67 Ho +8.01 68 Er +7.79 69 Tm +7.07 70 Yb +12.43 71 Lu +7.21 89 Ac 90 Th +10.31 91 Pa +9.10 92 U +8.42 93 Np +10.55 94 Pu +7.70 95 Am +8.30 96 Cm 97 Bk 98 Cf 99 Es 100 Fm 101 Md 102 No 103 Lr 57–71 89–103
Promethium Pm · Z = 61 · no stable isotope
+12.600 b coh / fm
19.95 σ coh / barn
168.4 σ abs / barn
61 X-ray f(0) / e
No stable isotope; value is for ¹⁴⁷Pm.
abs > 100 b — strong absorber
Values are real parts of the bound coherent scattering length for the natural isotope mixture, after V. F. Sears, Neutron News 3 , 26 (1992) and the NIST tabulation. For B, Cd, Sm, Eu, Gd and Dy, b is complex near thermal energies and the imaginary part is not shown; the violet ring flags where that matters. Elements with no stable isotope are drawn dashed, using long-lived or synthetic-sample values where one exists. Blank cells have no reliable tabulated value.