Both AMC and SKY read molecular data from files located in $RATRAN/molec, or an exact path specified in the keyword file amc.inp which is copied to the amc output file. Pure continuum calculations do not need such data files. For some molecules, the LAMDA database provides default files, but in general, users need to make their own data files. The spectroscopic databases at NASA-JPL and in Cologne provide energy levels, statistical weights and radiative decay rates. For collisional rate coefficients, consult NASA-GISS for the calculations of Sheldon Green, or the literature in this table for other work. Unfortunately, the literature on this subject is far from complete. If you know about calculations that are not in the table, please let us know!

The public distribution of ratran contains one example file (hco+.dat) in the molec directory.
If you need to make your own file, here is a detailed description of the required file format. The
format can be used for all molecules,
whether linear (HCO^{+}) or not (H_{2}O).
The lines that start with an exclamation mark (!) are not read by the program.

% Lines 1-2: molecule name

% Lines 3-4: molecular weight (a.m.u.)

% Lines 5-6: number of energy levels (NLEV)

% Lines 7-7+NLEV: level number, level energy (cm^{-1}), statistical weight.
These numbers may be followed by additional info such as the quantum numbers,
which are however not used by the program.
The levels must be listed in order of increasing energy.

% Lines 8+NLEV-9+NLEV: number of *radiative* transitions (NLIN)

% Lines 10+NLEV-10+NLEV+NLIN: transition number, upper level, lower level,
spontaneous decay rate (s^{-1}).
These numbers may be followed by additional info such as the line frequency,
which is however not used by the program.

% Lines 11+NLEV+NLIN-12+NLEV+NLIN: number of collision partners

% Lines 13+NLEV+NLIN-14+NLEV+NLIN: collision partner ID and reference. Valid identifications
are: 1=H2, 2=para-H2, 3=ortho-H2, 4=electrons, 5=H, 6=He.

% Lines 15+NLEV+NLIN-16+NLEV+NLIN: number of transitions for which collisional data exist (NCOL)

% Lines 17+NLEV+NLIN-18+NLEV+NLIN: number of temperatures for which collisional data exist

% Lines 19+NLEV+NLIN-20+NLEV+NLIN: values of temperatures for which collisional data exist

% Lines 21+NLEV+NLIN-21+NLEV+NLIN+NCOL: transition number, upper level, lower level;
rate coefficients (cm^{3}s^{-1}) at each temperature.
The program interpolates between rate coefficients in the specified
temperature range. Outside this range, it assumes the collisional de-excitation rate
coefficients are constant with T, i.e., it uses rate coefficients specified
at the highest T (400 K in this case)also for higher temperatures, and similarly
at temperatures below the lowest value (10 K in this case) for which rate coefficients were specified.

!MOLECULE

HCO+

!MOLECULAR WEIGHT

29.0

!NUMBER OF ENERGY LEVELS

21

!LEVEL + ENERGIES(cm^-1) + WEIGHT + J

1 0.000000000 1.0 0

2 2.975008479 3.0 1

21 624.269300464 41.0 20

!NUMBER OF RADIATIVE TRANSITIONS

20

!TRANS + UP + LOW + EINSTEINA(s^-1) + FREQ(GHz)

1 2 1 4.251e-05 89.18839570

2 3 2 4.081e-04 178.37481404

20 21 20 4.955e-01 1781.13802857

!NUMBER OF COLL PARTNERS

1

!COLLISIONS BETWEEN

1 H2-HCO+ from Flower (1999)

!NUMBER OF COLL TRANS

210

!NUMBER OF COLL TEMPS

12

!COLL TEMPS

10.0 20.0 30.0 50.0 70.0 100.0 150.0 200.0 250.0 300.0 350.0 400.0

!TRANS + UP + LOW + COLLRATES(cm^3 s^-1)

1 2 1 2.6e-10 2.3e-10 2.1e-10 2.0e-10 1.9e-10 1.8e-10 2.0e-10 2.2e-10 2.3e-10 2.5e-10 2.7e-10 2.8e-10

2 3 1 1.4e-10 1.2e-10 1.1e-10 1.0e-10 9.2e-11 8.8e-11 8.4e-11 8.2e-11 8.1e-11 8.3e-11 8.1e-11 8.5e-11

210 21 20 3.7e-10 3.6e-10 3.6e-10 3.5e-10 3.5e-10 3.5e-10 3.8e-10 4.0e-10 4.4e-10 4.7e-10 5.0e-10 5.2e-10