Utility

rascal.util.edlen_refraction(wavelengths, temperature, pressure, vapour_partial_pressure)[source]

Appendix A.IV of https://emtoolbox.nist.gov/Wavelength/Documentation.asp

rascal.util.filter_intensity(lines, min_intensity=0)[source]

Filters a line list by an intensity threshold

Parameters

  • lines (list[tuple (str, float, float)]) – A list of input lines where the 2nd parameter is intensity

  • min_intensity (int) – Intensity threshold

Returns

lines – Filtered line list

Return type

list

rascal.util.filter_separation(wavelengths, min_separation=0)[source]

Filters a wavelength list by a separation threshold.

Parameters

  • wavelengths (list) – List of input wavelengths

  • min_separation (int) – Separation threshold, Ansgtrom

Returns

distance_mask – Mask of values which satisfy the separation criteria

Return type

list

rascal.util.filter_wavelengths(lines, min_atlas_wavelength, max_atlas_wavelength)[source]

Filters a wavelength list to a minimum and maximum range.

Parameters

  • lines (list) – List of input wavelengths

  • min_atlas_wavelength (int) – Min wavelength, Ansgtrom

  • max_atlas_wavelength (int) – Max wavelength, Angstrom

Returns

lines – Filtered wavelengths within specified range limit

Return type

list

rascal.util.gauss(x, a, x0, sigma)[source]

1D Gaussian

Parameters

  • x – value or values to evaluate the Gaussian at

  • a (float) – Magnitude

  • x0 (float) – Gaussian centre

  • sigma (float) – Standard deviation (spread)

Returns

out – The Gaussian function evaluated at provided x

Return type

list

rascal.util.get_vapour_partial_pressure(relative_humidity, vapour_pressure)[source]

Appendix A.II of https://emtoolbox.nist.gov/Wavelength/Documentation.asp

rascal.util.get_vapour_pressure(temperature)[source]

Appendix A.I of https://emtoolbox.nist.gov/Wavelength/Documentation.asp

rascal.util.load_calibration_lines(elements=[], min_atlas_wavelength=3000, max_atlas_wavelength=15000, min_intensity=10, min_distance=10, vacuum=False, pressure=101325.0, temperature=273.15, relative_humidity=0.0)[source]

Load calibration lines from the standard NIST atlas. Rascal provides a cleaned set of NIST lines that can be used for general purpose calibration. It is recommended however that for repeated and robust calibration, the user should specify an instrument-specific atlas.

Provide a wavelength range suitable to your calibration source. You can also specify a minimum intensity that corresponds to the values listed in the NIST tables.

If you want air wavelengths (default), you can provide atmospheric conditions for your system. In most cases the default values of standard temperature and pressure should be sufficient.

Parameters

  • elements (list) – List of short element names, e.g. He as per NIST

  • min_atlas_wavelength (int) – Minimum wavelength to search, Angstrom

  • max_atlas_wavelength (int) – Maximum wavelength to search, Angstrom

  • min_intensity (int) – Minimum intensity to search, per NIST

  • max_intensity (int) – Maximum intensity to search, per NIST

  • vacuum (bool) – Return vacuum wavelengths

  • pressure (float) – Atmospheric pressure, Pascal

  • temperature (float) – Temperature in Kelvin, default room temp

  • relative_humidity (float) – Relative humidity, percent

Returns

out – Emission lines corresponding to the parameters specified

Return type

list

rascal.util.refine_peaks(spectrum, peaks, window_width=10, distance=None)[source]

Refine peak locations in a spectrum from a set of initial estimates.

This function attempts to fit a Gaussian to each peak in the provided list. It returns a list of sub-pixel refined peaks. If two peaks are very close, they can be refined to the same location. In this case only one of the peaks will be returned - i.e. this function will return a unique set of peak locations.

Parameters

  • spectrum (list) – Input spectrum (list of intensities)

  • peaks (list) – A list of peak locations in pixels

  • window_width (int) – Size of window to consider in fit either side of initial peak location

Returns

refined_peaks – A list of refined peak locations

Return type

list

rascal.util.vacuum_to_air_wavelength(wavelengths, temperature=273.15, pressure=101325, relative_humidity=0)[source]

The conversion follows the Modified Edlén Equations

https://emtoolbox.nist.gov/Wavelength/Documentation.asp

pressure drops by ~10% per 1000m above sea level temperature depends heavily on the location relative humidity is between 0-100, depends heavily on the location

Parameters

  • wavelengths (float or numpy.array) – Wavelengths in vacuum

  • temperature (float) – In unit of Kelvin

  • pressure (float) – In unit of Pa

  • relative_humidity (float) – Unitless in percentage (i.e. 0 - 100)

Returns

air wavelengths – The wavelengths in air given the condition

Return type

float or numpy.array