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- Atomic Line List (`astroquery.atomic`)

# Atomic Line List (`astroquery.atomic`)

## Getting started

“Atomic Line List” is a collection of more than 900,000 atomic transitions in the range from 0.5 Å to 1000 µm (source). `AtomicLineList` has 13 parameters of which all are optional. In the example below, only a restricted set of the available parameters is used to keep it simple: `wavelength_range`, `wavelength_type`, `wavelength_accuracy` and `element_spectrum`. The respective web form for Atomic Line List can be found at https://linelist.pa.uky.edu/atomic/. As can be seen there, the first form fields are “Wavelength range” and “Unit”. Because astroquery encourages the usage of AstroPy units, the expected type for the parameter `wavelength_range` is a tuple with two AstroPy quantities in it. This has the positive side-effect that even more units will be supported than by just using the web form directly.

In the following Python session you can see the `atomic` package in action. Note that Hz is actually not a supported unit by Atomic Line List, the atomic package takes care to support all spectral units.

    >>> from astropy import units as u
    >>> from astroquery.atomic import AtomicLineList
    >>> wavelength_range = (15 * u.nm, 1.5e+16 * u.Hz)
    >>> AtomicLineList.query_object(wavelength_range=wavelength_range, wavelength_type='Air',
    ...                             wavelength_accuracy=20, element_spectrum='C II-IV')
    <Table length=3>
    LAMBDA VAC ANG SPECTRUM  TT  ...  J J      A_ki    LEVEL ENERGY  CM 1
       float64       str4   str2 ...  str5   float64         str18
    -------------- -------- ---- ... ----- ----------- ------------------
          196.8874     C IV   E1 ... 1/2-*  91300000.0 0.00 -   507904.40
          197.7992     C IV   E1 ... 1/2-* 118000000.0 0.00 -   505563.30
          199.0122     C IV   E1 ... 1/2-* 157000000.0 0.00 -   502481.80

## Troubleshooting

If you are repeatedly getting failed queries, or bad/out-of-date results, try clearing your cache:

    >>> from astroquery.atomic import AtomicLineList
    >>> AtomicLineList.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

### astroquery.atomic Package

#### Classes

`AtomicLineListClass`() |
`Transition`() |