.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "api/gallery/spectro/atomic/plot_02_kirchhoff_bunsen_flame_spectra.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

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

        :ref:`Go to the end <sphx_glr_download_api_gallery_spectro_atomic_plot_02_kirchhoff_bunsen_flame_spectra.py>`
        to download the full example code.

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

.. _sphx_glr_api_gallery_spectro_atomic_plot_02_kirchhoff_bunsen_flame_spectra.py:


Kirchhoff and Bunsen's flame spectra: bright emission lines and matching dark absorption lines
===============================================================================================

Bunsen and Kirchhoff (1859-1861) vaporized salts in a nearly colourless
flame and found that each element gives bright lines at its own fixed
wavelengths. The top panel shows the strongest visible and near-visible
resonance lines of the alkali metals they studied, including caesium's
blue doublet and rubidium's red and near-infrared lines, the lines that
revealed those two new elements. The bottom panel illustrates
Kirchhoff's law: a cooler sodium vapour placed in front of a continuous
source absorbs at exactly the wavelengths where hot sodium emits. This
is what explains Fraunhofer's D lines.

.. GENERATED FROM PYTHON SOURCE LINES 17-35

.. code-block:: Python

    import matplotlib.pyplot as plt
    import numpy as np

    from chemistrykit.spectro.core.base_system import Spectrum

    # Strongest resonance lines (air wavelengths, nm) with rough relative intensities.
    elements = {
        "Li": Spectrum(positions=[670.8], intensities=[1.0]),
        "Na": Spectrum(positions=[589.0, 589.6], intensities=[1.0, 0.5]),
        "K": Spectrum(positions=[766.5, 769.9], intensities=[1.0, 0.5]),
        "Rb": Spectrum(positions=[780.0, 794.8], intensities=[1.0, 0.5]),
        "Cs": Spectrum(positions=[455.5, 459.3], intensities=[1.0, 0.45]),
    }
    colors = {"Li": "crimson", "Na": "orange", "K": "purple", "Rb": "darkred", "Cs": "royalblue"}

    for name, spectrum in elements.items():
        print(f"{name:>2s} emission lines (nm): {spectrum.positions}")





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

 .. code-block:: none

    Li emission lines (nm): [670.8]
    Na emission lines (nm): [589.  589.6]
     K emission lines (nm): [766.5 769.9]
    Rb emission lines (nm): [780.  794.8]
    Cs emission lines (nm): [455.5 459.3]




.. GENERATED FROM PYTHON SOURCE LINES 36-39

Kirchhoff's law of emission and absorption for sodium: hot sodium
vapour gives bright lines, while cooler vapour in front of a continuous
source removes light at the same two wavelengths.

.. GENERATED FROM PYTHON SOURCE LINES 39-49

.. code-block:: Python


    wavelength = np.linspace(586.0, 593.0, 3000)
    na = elements["Na"]
    emission = na.broaden(wavelength, shape="gaussian", fwhm=0.12)
    absorption_spectrum = np.ones_like(wavelength) * np.exp(-0.25 * na.broaden(wavelength, shape="gaussian", fwhm=0.12))

    emission_peaks = [wavelength[np.argmax(np.where(np.abs(wavelength - p) < 0.2, emission, 0.0))] for p in na.positions]
    absorption_dips = [wavelength[np.argmin(np.where(np.abs(wavelength - p) < 0.2, absorption_spectrum, 2.0))] for p in na.positions]
    print(f"Na emission peaks at {np.round(emission_peaks, 2)} nm, absorption dips at {np.round(absorption_dips, 2)} nm")





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

 .. code-block:: none

    Na emission peaks at [589.  589.6] nm, absorption dips at [589.  589.6] nm




.. GENERATED FROM PYTHON SOURCE LINES 50-67

.. code-block:: Python

    fig, (ax1, ax2) = plt.subplots(2, 1, figsize=(10, 7))
    for name, spectrum in elements.items():
        ax1.vlines(spectrum.positions, 0.0, spectrum.intensities, color=colors[name], lw=2, label=name)
    ax1.set_xlim(440.0, 810.0)
    ax1.set_xlabel("wavelength (nm)")
    ax1.set_ylabel("relative intensity")
    ax1.set_title("Flame emission lines: each element has its own fixed lines")
    ax1.legend(ncol=5)

    ax2.plot(wavelength, emission / emission.max(), color="orange", label="hot Na vapour: emission")
    ax2.plot(wavelength, absorption_spectrum, color="black", label="continuum through cooler Na: absorption")
    ax2.set_xlabel("wavelength (nm)")
    ax2.set_ylabel("relative intensity")
    ax2.set_title("Kirchhoff's law: emission and absorption at the same wavelengths (Na D lines)")
    ax2.legend(loc="center right")
    fig.tight_layout()
    plt.show()



.. image-sg:: /api/gallery/spectro/atomic/images/sphx_glr_plot_02_kirchhoff_bunsen_flame_spectra_001.png
   :alt: Flame emission lines: each element has its own fixed lines, Kirchhoff's law: emission and absorption at the same wavelengths (Na D lines)
   :srcset: /api/gallery/spectro/atomic/images/sphx_glr_plot_02_kirchhoff_bunsen_flame_spectra_001.png
   :class: sphx-glr-single-img






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

   **Total running time of the script:** (0 minutes 0.084 seconds)


.. _sphx_glr_download_api_gallery_spectro_atomic_plot_02_kirchhoff_bunsen_flame_spectra.py:

.. only:: html

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

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

      :download:`Download Jupyter notebook: plot_02_kirchhoff_bunsen_flame_spectra.ipynb <plot_02_kirchhoff_bunsen_flame_spectra.ipynb>`

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

      :download:`Download Python source code: plot_02_kirchhoff_bunsen_flame_spectra.py <plot_02_kirchhoff_bunsen_flame_spectra.py>`

    .. container:: sphx-glr-download sphx-glr-download-zip

      :download:`Download zipped: plot_02_kirchhoff_bunsen_flame_spectra.zip <plot_02_kirchhoff_bunsen_flame_spectra.zip>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_