*SPECTRUM files description: complex spectrum*

Each spectrum export directory contains 5 files (in addition to this one):

The name of the directory and of all the files begins with the same root ('spectrum-root') that abbreviate the types of spectrum and sample and the value of the varying parameter, if any.
This will allow you to always know which file belongs to a given spectrum (so you can put them all in the same directory without mixing them).

* The spectrum thumbnail file: 'spectrum-root'.micron.thumbnail.png, or 'spectrum-root'.cm-1.thumbnail.png, ...
  - provides a preview of the spectrum in its original units

* The spectrum data file: 'spectrum-root'.data.csv (or .asc, ...)
  - contains the spectral data (spectral position, intensity) and possibly the intensity error(s)) and a quality flag.

	The file header has 3 lines in the standard choice "Data type" = 'spectrum with column name and units'
	  - line 1: number of spectral points
	  - line 2: type of complex spectrum and its unit: type of real and imaginary parts of the complex spectrum (no intensity unit means intensity has no unit)
	The file may have up to 9 columns (separated with ',' or 'tab') described in the line above the data:
	  - line 3: the name of the columns: 'position(unit)', 'real_part', 'imaginary_part', 'err_real', 'err_imag' (or {'err_minus_real', 'err_plus_real', 'err_minus_imag', 'err_plus_imag'}, or {'real_min', 'real_max', 'imag_min', 'imag_max'}), 'quality_real', 'quality_imag'
		- column 1: 'position' will be one of {wavenumber, wavelength, frequency, energy} and 'unit' one of {m-1, cm-1, angstrom, nm, micron, mm, m, km, Hz, kHz, MHz, GHz, eV, keV}
		- column 2: 'real_part': the intensity of the real part of the complex spectrum
		- column 3: 'imaginary_part': the intensity of the imaginary part of the complex spectrum
		- columns 4 & 5: 'err_real', 'err_imag': error (symmetric, +/-) on real and imaginary parts
		  - or columns 4 to 7: 'err_minus_real'/_plus_real', and 'err_minus_imag'/'_plus_imag': negative and positive errors on real and imaginary parts
		  - or columns 4 to 7: 'real_min', 'real_max', and 'imag_min', 'imag_max': minimum and maximum values of the real and imaginary parts
		- columns 6 & 7 or 8 & 9:'quality_real', 'quality_imag': flag of quality, generally between 0 and 5 (0: 'no data' to 5: excellent data)
	  - lines 4 and following: the numerical data of the complex spectrum

* The spectrum metadata file : 'spectrum-root'.spectrum.html
* The sample metadata file : 'spectrum-root'.sample.html
  - They contain all the metadata of the spectrum and its sample (with its complete structure).
  - They contain active links to all associated metadata (instrument, experimentalists, publication, ...) as in the SSHADE web site.

* The citation file: 'spectrum-root'.citations.txt
  - Gives:
	- the general rules for SSHADE data use,
	- the DOI of the data
	- the full data reference (to be cited in papers),
	- the reference of the original paper(s) associated with this data (to be cited in papers).