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.. _astroquery.nist:
********************************
NIST Queries (`astroquery.nist`)
********************************
Tool to query the NIST Atomic Lines database (https://physics.nist.gov/PhysRefData/ASD/lines_form.html).
Getting started
===============
This is a relatively simple module that you may use to query spectra from
NIST. All the results are returned as a `~astropy.table.Table`. To do this you
just need to specify the lower and the upper wavelength for the spectrum you
want to fetch. These wavelengths must be specified as an appropriate
`~astropy.units.Quantity` object, for instance having units of
nanometer, or angstrom or the like. For example, to use a lower wavelength
value of 4000 Angstroms, you should use ```4000 * u.AA``` and if you want the
same in nanometers, just use ```400 * u.nm```. Of course there are several optional
parameters you can also specify. For instance use the ``linename`` parameter to
specify the spectrum you wish to fetch.
``linename`` also accepts multiple line strings in an iterable (e.g. ``["Na", "H I"]``)
or you can specify multiple lines as a single string value separated with a
semicolon (e.g. ``"Na;Mg"``). Now let's see a simple example:
.. doctest-remote-data::
>>> from astroquery.nist import Nist
>>> import astropy.units as u
>>> table = Nist.query(4000 * u.AA, 7000 * u.AA, linename="H I")
>>> print(table)
Observed Ritz Transition Rel. ... Type TP Line
------------- ------------- ------------- ------ ... ---- ----- --------
-- 4102.85985517 24373.2429403 -- ... -- T7771 --
-- 4102.86191087 24373.2307283 -- ... -- T7771 --
-- 4102.8632 24373.223 -- ... -- -- c57
4102.86503488 4102.86503481 24373.2121704 -- ... E2 -- L11759
-- 4102.86579132 24373.2076763 -- ... -- T7771 --
4102.86785081 4102.86785074 24373.1954423 -- ... M1 -- L11759
-- 4102.8680725 24373.1941249 -- ... -- T7771 --
4102.892 4102.8991 24373.05 70000 ... -- T8637 L7436c29
-- 4102.8922 24373.051 -- ... -- -- c58
-- 4102.92068748 24372.8815683 -- ... -- T7771 --
... ... ... ... ... ... ... ...
-- 6564.564672 15233.302588 -- ... -- T7771 --
-- 6564.579878 15233.267302 -- ... M1 -- --
-- 6564.583 15233.26 -- ... -- -- c66
6564.584404 6564.584403 15233.256799 -- ... -- T7771 L6891c38
6564.6 6564.632 15233.21 500000 ... -- T8637 L7400c29
-- 6564.608 15233.202 -- ... -- -- c69
6564.66464 6564.66466 15233.07061 -- ... -- T7771 L2752
-- 6564.6662 15233.067 -- ... -- -- c71
-- 6564.667 15233.065 -- ... -- -- c70
-- 6564.680232 15233.034432 -- ... -- T7771 --
-- 6564.722349 15232.9367 -- ... -- T7771 --
Length = 53 rows
Note that using a different unit will result in different output units in the
``Observed`` and ``Ritz`` columns.
There are several other optional parameters that you may also set. For instance
you may set the ``energy_level_unit`` to any one of these values. ::
'R' 'Rydberg' 'rydberg' 'cm' 'cm-1' 'EV' 'eV' 'electronvolt' 'ev' 'invcm'
Similarly you can set the ``output_order`` to any one of 'wavelength' or
'multiplet'. A final parameter you may also set is the ``wavelength_type`` to one of 'vacuum'
or 'vac+air'. Here is an example with all these parameters.
.. doctest-remote-data::
>>> from astroquery.nist import Nist
>>> table = Nist.query(4000 * u.nm, 7000 * u.nm, linename='H I',
... energy_level_unit='eV', output_order='wavelength',
... wavelength_type='vacuum')
>>> print(table) # doctest: +IGNORE_OUTPUT
Observed Ritz Transition Rel. Aki ... gi gk Type TP Line
-------- ----------- ----------- ----- --------- ... --------- ---- ----- -----
-- 4020.871 2487.024 (200) 5526.5 ... 72 - 392 -- T8637 --
-- 4052.18664 2467.803411 -- 1238100.0 ... 2 - 4 -- T7771 --
-- 4052.19376 2467.79907 -- 737160.0 ... 2 - 4 -- T7771 --
-- 4052.22121 2467.78236 -- 215030.0 ... 2 - 2 -- T7771 --
-- 4052.23222 2467.77565 -- 737210.0 ... 2 - 2 -- T7771 --
-- 4052.248747 2467.765585 -- 2412100.0 ... 4 - 6 -- T7771 --
-- 4052.24892 2467.765479 -- 1485800.0 ... 4 - 6 -- T7771 --
-- 4052.26147 2467.75784 -- 18846.0 ... 4 - 4 -- T7771 --
-- 4052.26174 2467.757676 -- 247630.0 ... 4 - 4 -- T7771 --
-- 4052.26738 2467.75424 -- 4102300.0 ... 6 - 8 -- T7771 --
... ... ... ... ... ... ... ... ... ...
5128.65 5128.662 1949.83 (450) 36881.0 ... 72 - 200 -- T8637 L7452
-- 5169.282 1934.5047 -- 984.98 ... 98 - 722 -- T8637 --
-- 5263.685 1899.8096 -- 1312.1 ... 98 - 648 -- T8637 --
-- 5379.776 1858.8134 -- 1781.2 ... 98 - 578 -- T8637 --
-- 5525.19 1809.8925 (150) 2470.9 ... 98 - 512 -- T8637 --
-- 5711.464 1750.8646 (180) 3515.8 ... 98 - 450 -- T8637 --
-- 5908.22 1692.5572 (540) 70652.0 ... 72 - 162 -- T8637 --
-- 5956.845 1678.7409 (210) 5156.2 ... 98 - 392 -- T8637 --
-- 6291.918 1589.3405 (250) 7845.7 ... 98 - 338 -- T8637 --
-- 6771.993 1476.6701 (300) 12503.0 ... 98 - 288 -- T8637 --
-- 6946.756 1439.5208 -- 688.58 ... 128 - 800 -- T8637 --
Length = 37 rows
Troubleshooting
===============
If you are repeatedly getting failed queries, or bad/out-of-date results, try clearing your cache:
.. code-block:: python
>>> from astroquery.nist import Nist
>>> Nist.clear_cache()
If this function is unavailable, upgrade your version of astroquery.
The ``clear_cache`` function was introduced in version 0.4.7.dev8479.
Reference/API
=============
.. automodapi:: astroquery.nist
:no-inheritance-diagram:
|
