# Isotopic abundances from M. Berglund and M. E. Wieser, "Isotopic compositions
# of the elements 2009 (IUPAC Technical Report)", Pure. Appl. Chem. 83 (2),
# pp. 397--410 (2011).
natural_abundance = {
    'H-1': 0.999885, 'H-2': 0.000115, 'He-3': 1.34e-06,
    'He-4': 0.99999866, 'Li-6': 0.0759, 'Li-7': 0.9241,
    'Be-9': 1.0, 'B-10': 0.199, 'B-11': 0.801,
    'C-12': 0.9893, 'C-13': 0.0107, 'N-14': 0.99636,
    'N-15': 0.00364, 'O-16': 0.99757, 'O-17': 0.00038,
    'O-18': 0.00205, 'F-19': 1.0, 'Ne-20': 0.9048,
    'Ne-21': 0.0027, 'Ne-22': 0.0925, 'Na-23': 1.0,
    'Mg-24': 0.7899, 'Mg-25': 0.1, 'Mg-26': 0.1101,
    'Al-27': 1.0, 'Si-28': 0.92223, 'Si-29': 0.04685,
    'Si-30': 0.03092, 'P-31': 1.0, 'S-32': 0.9499,
    'S-33': 0.0075, 'S-34': 0.0425, 'S-36': 0.0001,
    'Cl-35': 0.7576, 'Cl-37': 0.2424, 'Ar-36': 0.003336,
    'Ar-38': 0.000629, 'Ar-40': 0.996035, 'K-39': 0.932581,
    'K-40': 0.000117, 'K-41': 0.067302, 'Ca-40': 0.96941,
    'Ca-42': 0.00647, 'Ca-43': 0.00135, 'Ca-44': 0.02086,
    'Ca-46': 4e-05, 'Ca-48': 0.00187, 'Sc-45': 1.0,
    'Ti-46': 0.0825, 'Ti-47': 0.0744, 'Ti-48': 0.7372,
    'Ti-49': 0.0541, 'Ti-50': 0.0518, 'V-50': 0.0025,
    'V-51': 0.9975, 'Cr-50': 0.04345, 'Cr-52': 0.83789,
    'Cr-53': 0.09501, 'Cr-54': 0.02365, 'Mn-55': 1.0,
    'Fe-54': 0.05845, 'Fe-56': 0.91754, 'Fe-57': 0.02119,
    'Fe-58': 0.00282, 'Co-59': 1.0, 'Ni-58': 0.68077,
    'Ni-60': 0.26223, 'Ni-61': 0.011399, 'Ni-62': 0.036346,
    'Ni-64': 0.009255, 'Cu-63': 0.6915, 'Cu-65': 0.3085,
    'Zn-64': 0.4917, 'Zn-66': 0.2773, 'Zn-67': 0.0404,
    'Zn-68': 0.1845, 'Zn-70': 0.0061, 'Ga-69': 0.60108,
    'Ga-71': 0.39892, 'Ge-70': 0.2057, 'Ge-72': 0.2745,
    'Ge-73': 0.0775, 'Ge-74': 0.365, 'Ge-76': 0.0773,
    'As-75': 1.0, 'Se-74': 0.0089, 'Se-76': 0.0937,
    'Se-77': 0.0763, 'Se-78': 0.2377, 'Se-80': 0.4961,
    'Se-82': 0.0873, 'Br-79': 0.5069, 'Br-81': 0.4931,
    'Kr-78': 0.00355, 'Kr-80': 0.02286, 'Kr-82': 0.11593,
    'Kr-83': 0.115, 'Kr-84': 0.56987, 'Kr-86': 0.17279,
    'Rb-85': 0.7217, 'Rb-87': 0.2783, 'Sr-84': 0.0056,
    'Sr-86': 0.0986, 'Sr-87': 0.07, 'Sr-88': 0.8258,
    'Y-89': 1.0, 'Zr-90': 0.5145, 'Zr-91': 0.1122,
    'Zr-92': 0.1715, 'Zr-94': 0.1738, 'Zr-96': 0.028,
    'Nb-93': 1.0, 'Mo-92': 0.1453, 'Mo-94': 0.0915,
    'Mo-95': 0.1584, 'Mo-96': 0.1667, 'Mo-97': 0.096,
    'Mo-98': 0.2439, 'Mo-100': 0.0982, 'Ru-96': 0.0554,
    'Ru-98': 0.0187, 'Ru-99': 0.1276, 'Ru-100': 0.126,
    'Ru-101': 0.1706, 'Ru-102': 0.3155, 'Ru-104': 0.1862,
    'Rh-103': 1.0, 'Pd-102': 0.0102, 'Pd-104': 0.1114,
    'Pd-105': 0.2233, 'Pd-106': 0.2733, 'Pd-108': 0.2646,
    'Pd-110': 0.1172, 'Ag-107': 0.51839, 'Ag-109': 0.48161,
    'Cd-106': 0.0125, 'Cd-108': 0.0089, 'Cd-110': 0.1249,
    'Cd-111': 0.128, 'Cd-112': 0.2413, 'Cd-113': 0.1222,
    'Cd-114': 0.2873, 'Cd-116': 0.0749, 'In-113': 0.0429,
    'In-115': 0.9571, 'Sn-112': 0.0097, 'Sn-114': 0.0066,
    'Sn-115': 0.0034, 'Sn-116': 0.1454, 'Sn-117': 0.0768,
    'Sn-118': 0.2422, 'Sn-119': 0.0859, 'Sn-120': 0.3258,
    'Sn-122': 0.0463, 'Sn-124': 0.0579, 'Sb-121': 0.5721,
    'Sb-123': 0.4279, 'Te-120': 0.0009, 'Te-122': 0.0255,
    'Te-123': 0.0089, 'Te-124': 0.0474, 'Te-125': 0.0707,
    'Te-126': 0.1884, 'Te-128': 0.3174, 'Te-130': 0.3408,
    'I-127': 1.0, 'Xe-124': 0.000952, 'Xe-126': 0.00089,
    'Xe-128': 0.019102, 'Xe-129': 0.264006, 'Xe-130': 0.04071,
    'Xe-131': 0.212324, 'Xe-132': 0.269086, 'Xe-134': 0.104357,
    'Xe-136': 0.088573, 'Cs-133': 1.0, 'Ba-130': 0.00106,
    'Ba-132': 0.00101, 'Ba-134': 0.02417, 'Ba-135': 0.06592,
    'Ba-136': 0.07854, 'Ba-137': 0.11232, 'Ba-138': 0.71698,
    'La-138': 0.0008881, 'La-139': 0.9991119, 'Ce-136': 0.00185,
    'Ce-138': 0.00251, 'Ce-140': 0.8845, 'Ce-142': 0.11114,
    'Pr-141': 1.0, 'Nd-142': 0.27152, 'Nd-143': 0.12174,
    'Nd-144': 0.23798, 'Nd-145': 0.08293, 'Nd-146': 0.17189,
    'Nd-148': 0.05756, 'Nd-150': 0.05638, 'Sm-144': 0.0307,
    'Sm-147': 0.1499, 'Sm-148': 0.1124, 'Sm-149': 0.1382,
    'Sm-150': 0.0738, 'Sm-152': 0.2675, 'Sm-154': 0.2275,
    'Eu-151': 0.4781, 'Eu-153': 0.5219, 'Gd-152': 0.002,
    'Gd-154': 0.0218, 'Gd-155': 0.148, 'Gd-156': 0.2047,
    'Gd-157': 0.1565, 'Gd-158': 0.2484, 'Gd-160': 0.2186,
    'Tb-159': 1.0, 'Dy-156': 0.00056, 'Dy-158': 0.00095,
    'Dy-160': 0.02329, 'Dy-161': 0.18889, 'Dy-162': 0.25475,
    'Dy-163': 0.24896, 'Dy-164': 0.2826, 'Ho-165': 1.0,
    'Er-162': 0.00139, 'Er-164': 0.01601, 'Er-166': 0.33503,
    'Er-167': 0.22869, 'Er-168': 0.26978, 'Er-170': 0.1491,
    'Tm-169': 1.0, 'Yb-168': 0.00123, 'Yb-170': 0.02982,
    'Yb-171': 0.1409, 'Yb-172': 0.2168, 'Yb-173': 0.16103,
    'Yb-174': 0.32026, 'Yb-176': 0.12996, 'Lu-175': 0.97401,
    'Lu-176': 0.02599, 'Hf-174': 0.0016, 'Hf-176': 0.0526,
    'Hf-177': 0.186, 'Hf-178': 0.2728, 'Hf-179': 0.1362,
    'Hf-180': 0.3508, 'Ta-180': 0.0001201, 'Ta-181': 0.9998799,
    'W-180': 0.0012, 'W-182': 0.265, 'W-183': 0.1431,
    'W-184': 0.3064, 'W-186': 0.2843, 'Re-185': 0.374,
    'Re-187': 0.626, 'Os-184': 0.0002, 'Os-186': 0.0159,
    'Os-187': 0.0196, 'Os-188': 0.1324, 'Os-189': 0.1615,
    'Os-190': 0.2626, 'Os-192': 0.4078, 'Ir-191': 0.373,
    'Ir-193': 0.627, 'Pt-190': 0.00012, 'Pt-192': 0.00782,
    'Pt-194': 0.3286, 'Pt-195': 0.3378, 'Pt-196': 0.2521,
    'Pt-198': 0.07356, 'Au-197': 1.0, 'Hg-196': 0.0015,
    'Hg-198': 0.0997, 'Hg-199': 0.1687, 'Hg-200': 0.231,
    'Hg-201': 0.1318, 'Hg-202': 0.2986, 'Hg-204': 0.0687,
    'Tl-203': 0.2952, 'Tl-205': 0.7048, 'Pb-204': 0.014,
    'Pb-206': 0.241, 'Pb-207': 0.221, 'Pb-208': 0.524,
    'Bi-209': 1.0, 'Th-232': 1.0, 'Pa-231': 1.0,
    'U-234': 5.4e-05, 'U-235': 0.007204, 'U-238': 0.992742
}