See populations of computed levels

Spectrum methods gives you access to the populations of levels used in a nonequilibrium spectrum :

• get_populations() provides the populations

of all levels of the molecule, used to compute the nonequilibrium partition function

• lines returns all informations

of the visible lines, in particular the populations of the upper and lower levels of absorbing/emitting lines in the spectrum.

from astropy import units as u

We first compute a noneq CO spectrum. Notice the keys export_lines=True and export_populations=True

from radis import calc_spectrum

s = calc_spectrum(
    1900 / u.cm,
    2300 / u.cm,
    molecule="CO",
    isotope="1",
    pressure=1.01325 * u.bar,
    Tvib=3000 * u.K,
    Trot=1000 * u.K,
    mole_fraction=0.1,
    path_length=1 * u.cm,
    databank="hitran",  # or 'hitemp', 'geisa', 'exomol'
    export_lines=True,
    export_populations="rovib",
)

/home/docs/checkouts/readthedocs.org/user_builds/radis/checkouts/latest/radis/io/hitran.py:170: AccuracyWarning:

All columns are not downloaded currently, please use cache = 'regen' and extra_params='all' to download all columns.

/home/docs/checkouts/readthedocs.org/user_builds/radis/checkouts/latest/radis/misc/warning.py:427: HighTemperatureWarning:

HITRAN is valid for low temperatures (typically < 700 K). For higher temperatures you may need HITEMP or CDSD. See the 'databank=' parameter

Calculating Non-Equilibrium Spectrum
Physical Conditions
----------------------------------------
   Tgas                 1000.0 K
   Trot                 1000.0 K
   Tvib                 3000.0 K
   isotope              1
   mole_fraction        0.1
   molecule             CO
   path_length          1.0 cm
   pressure             1.01325 bar
   rot_distribution     boltzmann
   self_absorption      True
   state                X
   vib_distribution     boltzmann
   wavenum_max          2300.0000 cm-1
   wavenum_min          1900.0000 cm-1
Computation Parameters
----------------------------------------
   Tref                 296 K
   add_at_used
   broadening_method    voigt
   cutoff               1e-27 cm-1/(#.cm-2)
   dbformat             hitran
   dbpath               /home/docs/.radisdb/hitran/CO.hdf5
   folding_thresh       1e-06
   include_neighbouring_lines  True
   memory_mapping_engine  auto
   neighbour_lines      0 cm-1
   optimization         simple
   parfuncfmt           hapi
   parsum_mode          full summation
   pseudo_continuum_threshold  0
   sparse_ldm           auto
   truncation           50 cm-1
   waveunit             cm-1
   wstep                0.01 cm-1
   zero_padding         -1
----------------------------------------
Fetching Evib & Erot.
/home/docs/checkouts/readthedocs.org/user_builds/radis/checkouts/latest/radis/misc/warning.py:427: NegativeEnergiesWarning:

There are negative rotational energies in the database

/home/docs/checkouts/readthedocs.org/user_builds/radis/checkouts/latest/radis/misc/warning.py:427: PerformanceWarning:

'gu' was recomputed although 'gp' already in DataFrame. All values are equal

/home/docs/checkouts/readthedocs.org/user_builds/radis/checkouts/latest/radis/misc/warning.py:427: PerformanceWarning:

'object' type column found in database, calculations and memory usage would be faster with a numeric type. Possible solution is to not use 'save_memory' and convert the columns to dtype.

... sorting lines by vibrational bands
... lines sorted in 0.0s
0.14s - Spectrum calculated

Below we plot the populations We could also have used plot_populations() directly

pops = s.get_populations("CO")["rovib"]

/home/docs/checkouts/readthedocs.org/user_builds/radis/checkouts/latest/radis/spectrum/spectrum.py:2410: UserWarning:

Populations valid for partition function calculation but sometimes NOT for spectra calculations, e.g. CO2.
                         See help on how to use 's.lines.query' instead, for instance in https://github.com/radis/radis/issues/508.
                         Turn off warning with 'show_warning=False'

Plot populations : Here we plot population fraction vs rotational number of the 2nd vibrational level v==2, for all levels as well as for levels of lines visible in the spectrum

import matplotlib.pyplot as plt

pops.query("v==2").plot(
    "j",
    "n",
    label="populations used to compute\n partition functions",
    style=".-",
    markersize=2,
)
s.lines.query("vl==2").plot(
    "jl",
    "nl",
    ax=plt.gca(),
    label="populations of visible\n absorbing lines",
    kind="scatter",
    color="r",
)
plt.xlim((0, 80))
plt.legend()

<matplotlib.legend.Legend object at 0x7f706e34f7c0>

Print all levels information

print(f"{len(pops)} levels ")
print(pops)
print(pops.columns)

7766 levels
       v   j             E  ...             n        Qrot      nrot
0      0   0      0.000000  ...  1.754208e-03  362.691791  0.002757
1      0   1      3.845033  ...  5.233590e-03  362.691791  0.008226
2      0   2     11.534953  ...  8.626674e-03  362.691791  0.013559
3      0   3     23.069466  ...  1.187857e-02  362.691791  0.018670
4      0   4     38.448131  ...  1.493823e-02  362.691791  0.023479
...   ..  ..           ...  ...           ...         ...       ...
7761  48  38  89299.135499  ...  2.237048e-21  360.424333  0.003612
7762  48  39  89447.643402  ...  1.853601e-21  360.424333  0.002993
7763  48  40  89599.882150  ...  1.526677e-21  360.424333  0.002465
7764  48  41  89755.845909  ...  1.249931e-21  360.424333  0.002018
7765  48  42  89915.528699  ...  1.017299e-21  360.424333  0.001643

[7766 rows x 13 columns]
Index(['v', 'j', 'E', 'Evib', 'viblvl', 'gj', 'gvib', 'grot', 'Erot', 'nvib',
       'n', 'Qrot', 'nrot'],
      dtype='object')

Print visible lines information :

print(f"{len(s.lines)} visible lines in the spectrum")
print(s.lines)
print(s.lines.columns)

274 visible lines in the spectrum
             wav           int      A  ...  hwhm_voigt  hwhm_lorentz  hwhm_gauss
0    1900.341956  3.539000e-29  12.45  ...    0.016713      0.015650    0.004067
1    1902.414114  2.295000e-31  24.91  ...    0.017474      0.016455    0.004072
2    1905.778633  9.041000e-29  12.54  ...    0.016872      0.015814    0.004079
3    1907.676341  5.311000e-31  25.11  ...    0.017672      0.016659    0.004083
4    1911.187699  2.268000e-28  12.64  ...    0.017028      0.015973    0.004091
..           ...           ...    ...  ...         ...           ...         ...
269  2291.548195  1.124000e-28  21.70  ...    0.017153      0.015650    0.004905
270  2293.336784  4.416000e-29  21.77  ...    0.017008      0.015491    0.004909
271  2295.082667  1.703000e-29  21.83  ...    0.016901      0.015372    0.004912
272  2296.785698  6.450000e-30  21.90  ...    0.016752      0.015208    0.004916
273  2298.445736  2.400000e-30  21.97  ...    0.016609      0.015049    0.004919

[274 rows x 55 columns]
Index(['wav', 'int', 'A', 'airbrd', 'selbrd', 'El', 'Tdpair', 'Pshft', 'ierr',
       'iref', 'line_mixing_flag', 'gp', 'gpp', 'Fu', 'branch', 'jl', 'syml',
       'Fl', 'vu', 'vl', 'ju', 'Eu', 'Evibl', 'Evibu', 'Erotu', 'Erotl', 'gju',
       'gjl', 'grotu', 'grotl', 'gvibu', 'gvibl', 'gu', 'gl', 'Rs2', 'Blu',
       'Bul', 'Aul', 'viblvl_l', 'viblvl_u', 'band', 'Qrotl', 'Qrotu',
       'nu_vib', 'nl_vib', 'nu_rot', 'nl_rot', 'nu', 'nl', 'S', 'Ei',
       'shiftwav', 'hwhm_voigt', 'hwhm_lorentz', 'hwhm_gauss'],
      dtype='object')

We can also look at unique levels; for instance sorting by quantum numbers v, J of the lower level : vl, jl

print(
    len(s.lines.groupby(["vl", "jl"])),
    " visible absorbing levels (i.e. unique 'vl', 'jl' ",
)

141  visible absorbing levels (i.e. unique 'vl', 'jl'

line_survey() is also a convenient way to explore populations and other line parameters, for instance

s.line_survey(overlay="absorbance", barwidth=0.001, lineinfo="all")