Isotope file

SPECTRUM fully supports the calculation of atomic and molecular isotopic spectra, although not in the default mode. To enable the isotope mode, use switch ``i''. This will cause SPECTRUM to prompt the user for an isotope file; the one provided in the distribution is isotope.iso. The types of information contained in this file can be understood from the following sample lines:

  1.0   1    1.007825  0.999885
  1.0   2    2.0140    0.000115
  2.0   3    3.016029  0.00000137
  2.0   4    4.002603  0.99999863
  3.0   6    6.015121  0.0759
  3.0   7    7.016003  0.9241
  4.0   9    9.012182  1.000
  4.0  10   10.013534  0.000
  5.0  10   10.012937  0.199
  5.0  11   11.009305  0.801
  6.0  12   12.000000  0.9893
  6.0  13   13.003355  0.0107

The first column gives the atomic code; 1.0 is for hydrogen, 2.0 for helium, etc. The second column gives the mass number for the isotope. Thus, 1.0 2 stands for deuterium, 6.0 13 for $^{13}$C. The third column gives the molecular weight for the isotope, and the fourth column the relative abundance in the solar system. So, for instance, in the solar system, 98.93% of carbon is $^{12}$C and 1.07% is $^{13}$C. Note that not all isotopes are represented in isotope.iso; $^{14}$C is a radioactive isotope of carbon with a short half-life ($\sim 5000$ years) and so should not be present with any significant abundance in the atmospheres of stars of any type. Thus, only astrophysically important isotopes are included in isotope.iso.

If the user is interested in calculating spectra with unusual isotopic abundances, then the relative abundances should be modified in isotope.iso. However, it is up to the user to compile the required spectral linelist. The spectral linelist used in the isotope mode has an additional column that specifies the mass number or ``isotope code'' for each spectral line. See §  for more information.

SPECTRUM supports a total of 310 isotopes, the ones listed in isotope.iso. SPECTRUM also supports molecules that involve isotopes. For instance, there are three astrophysically important versions of the C$_2$ molecule, $^{12}$C$^{12}$C, $^{13}$C$^{12}$C, and $^{13}$C$^{13}$C. Bandheads and individual molecular lines for these three isotopic versions of C$_2$ have slightly different wavelengths. The molecules currently supported in isotope mode, along with their ``isotope codes'' are listed below:

Molecule        Isotope Code
12C H               12
13C H               13
12C D                2
14N H               14
15N H               15
14N D                2
16O H               16
17O H               17
18O H               18
16O D                2
24Mg H              24
25Mg H              25
26Mg H              26
24Mg D               2
28Si H              28
29Si H              29
30Si H              30
28Si D               2
40Ca H              40
42Ca H              42
43Ca H              43
44Ca H              44
46Ca H              46
48Ca H              48
40Ca D               2
12C 12C             12
12C 13C             13
13C 13C             33
12C 14N             12
12C 15N             15
13C 14N             13
12C 16O             12
12C 17O             17
12C 18O             18
13C 16O             13
28Si 16O            16
29Si 16O            29
30Si 16O            30
28Si 17O            17
28Si 18O            18

Note: isotopes for H$_2$, TiO and ZrO are not yet supported. See §  for more detailed information.