.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "auto_examples/plot_linestrengths.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        Run this example online :

        - Click :ref:`here <sphx_glr_download_auto_examples_plot_linestrengths.py>`
          to download the full example code

        - Then start `Radis-Lab <https://radis.github.io/radis-lab/>`__,
          upload the Jupyter notebook, and run it from there.

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_auto_examples_plot_linestrengths.py:


================================================
Scale Linestrengths of carbon-monoxide
================================================

This example scales the linestrengths of CO to Tgas=300 from Tref = 296 and then plots
the linestrengths against the wavenumbers. We are using :py:func:`~radis.io.hitemp.fetch_hitemp`
function to retrieve the dataframe from the HITEMP-CO databank.

References
----------

.. math::
    S(T) = S_0 \frac{Q_{ref}}{Q_{gas}} \operatorname{exp}\left(-E_l \left(\frac{1}{T_{gas}}-\frac{1}{T_{ref}}\right)\right) \frac{1-\operatorname{exp}\left(\frac{-\omega_0}{Tgas}\right)}{1-\operatorname{exp}\left(\frac{-\omega_0}{T_{ref}}\right)}

See Eq.(A11) in [Rothman-1998]_

Similar functions are used directly at the hearth of RADIS's SpectrumFactory in the
:py:meth:`~radis.lbl.base.BaseFactory.calc_linestrength_eq` and :py:meth:`~radis.lbl.base.BaseFactory.calc_linestrength_noneq` methods

.. GENERATED FROM PYTHON SOURCE LINES 22-93



.. image-sg:: /auto_examples/images/sphx_glr_plot_linestrengths_001.png
   :alt: plot linestrengths
   :srcset: /auto_examples/images/sphx_glr_plot_linestrengths_001.png
   :class: sphx-glr-single-img


.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    Scaling equilibrium linestrength






|

.. code-block:: default


    from matplotlib import pyplot as plt
    from numpy import exp

    from radis.db.classes import get_molecule, get_molecule_identifier
    from radis.io.hitemp import fetch_hitemp
    from radis.levels.partfunc import PartFuncTIPS
    from radis.phys.constants import hc_k


    def get_Qgas(molecule, iso, T):

        M = get_molecule_identifier(molecule)

        Q = PartFuncTIPS(M, iso)
        return Q.at(T=T)


    def scale_linestrength_eq(df, Tref, Tgas):

        print("Scaling equilibrium linestrength")

        # %% Load partition function values

        def _calc_Q(molecule, iso, T_ref, T_gas):

            Qref = get_Qgas(molecule, iso, T_ref)
            Qgas = get_Qgas(molecule, iso, T_gas)

            return Qref, Qgas

        id_set = df.id.unique()
        id = list(id_set)[0]
        molecule = get_molecule(id)  # retrieve the molecule
        iso_set = set(df.iso)  # df1.iso.unique()

        Qref_Qgas_ratio = {}

        for iso in iso_set:
            Qref, Qgas = _calc_Q(molecule, iso, Tref, Tgas)
            Qref_Qgas_ratio[iso] = Qref / Qgas

        # Scaling linestrength with the equations from Rotham's paper
        line_strength = df.int * df["iso"].map(Qref_Qgas_ratio)
        line_strength *= exp(-hc_k * df.El * (1 / Tgas - 1 / Tref))
        line_strength *= (1 - exp(-hc_k * df.wav / Tgas)) / (1 - exp(-hc_k * df.wav / Tref))
        # Add a fresh columns with the scaled linestrength
        df["S"] = line_strength  # [cm-1/(molecules/cm-2)]

        # Just to make sure linestrength is indeed added
        assert "S" in df

        return df


    if __name__ == "__main__":
        Tref = 296
        df = fetch_hitemp(
            molecule="CO",
            isotope="1, 2, 3",
            load_wavenum_min=2000,
            load_wavenum_max=2250,
        )

        Tgas = 450

        df = scale_linestrength_eq(df, Tref, Tgas)
        plt.bar(df["wav"], df["S"])
        plt.xlabel("Wavenumbers in cm-1")
        plt.ylabel("Linestrengths in cm-1/(molecules/cm-2)")
        plt.show()


.. rst-class:: sphx-glr-timing

   **Total running time of the script:** ( 0 minutes  5.720 seconds)


.. _sphx_glr_download_auto_examples_plot_linestrengths.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example


    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: plot_linestrengths.py <plot_linestrengths.py>`

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: plot_linestrengths.ipynb <plot_linestrengths.ipynb>`