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- HITRAN Queries (`astroquery.hitran`)

# HITRAN Queries (`astroquery.hitran`)

## Getting started

This module provides an interface to the high-resolution transmission molecular absorption database API (HITRAN). The current version of the database contains a compilation of spectroscopic parameters for 49 molecular species along with their most significant isotopologues. Using the `hitran` module you can search transitions for a particular molecule in a given wavenumber range.

## Examples

This will download all transitions of the main isotopologue of water between the wavenumbers of 3400 and 4100 cm-1. The expected type for the parameters `min_frequency` and `max_frequency` is an AstroPy quantity. The data are returned as an `Table` instance.

    >>> from astropy import units as u
    >>> from astroquery.hitran import Hitran
    >>> tbl = Hitran.query_lines(molecule_number=1,
    ...                            isotopologue_number=1,
    ...                            min_frequency=0. / u.cm,
    ...                            max_frequency=10. / u.cm)
    >>> tbl
    <Table length=29>
    molec_id local_iso_id    nu        sw    ... line_mixing_flag    gp     gpp
     int32      int32     float32   float32  ...      bytes1      float32 float32
    -------- ------------ -------- --------- ... ---------------- ------- -------
           1            1 0.072049 1.875e-30 ...                      9.0    11.0
           1            1 0.400571 2.528e-28 ...                     27.0    21.0
           1            1 0.741682 4.451e-25 ...                     39.0    33.0
         ...          ...      ...       ... ...              ...     ...     ...
           1            1 9.640401 1.593e-34 ...                    129.0   123.0
           1            1 9.795592 1.794e-27 ...                     39.0    45.0
           1            1 9.834255 1.969e-35 ...                    135.0   141.0
           1            1 9.921502 6.136e-28 ...                     13.0    15.0

## Troubleshooting

If you are repeatedly getting failed queries, or bad/out-of-date results, try clearing your cache:

    >>> from astroquery.hitran import Hitran
    >>> Hitran.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.hitran Package

#### HITRAN Catalog Query Tool

Author:

  Adam Ginsburg (adam.g.ginsburg@gmail.com)

#### Classes

`HitranClass`(**kwargs) | Initialize a Hitran query class.