cond unit and Hitran cross-sections

[erwanp]

• Parse dimensioned values (i.e. with units) in Spectrum conditions

• Parse and generate Spectrum from manually downloaded HITRAN cross section files (https://hitran.org/xsc/)

• Add tests

• Add Gallery example

Note : this PR might raise errors when units are not defined in user-scripts; in particular path_length and pressure. Spectrum.cond_units should be used to define them.

---

from radis import Spectrum
from radis.phys.units import Unit as u

# Here we use a downloaded cross-section file from the test suite :
from radis.test.utils import getTestFile

datafile = getTestFile("CH3COCH3_233.4_375.2_700.0-1780.0_13.xsc")

# Temperature and pressure are given by the cross-section file used (above: 233.4 K; 375.2 Torr)
# Mole fraction and path length can be recomputed arbitrarily :
conditions = {"mole_fraction": 0.1, "path_length": 20 * u("mm")}

s = Spectrum.from_xsc(datafile, conditions)

s.plot("transmittance_noslit", lw=2)

# Rescale for other path lengths, and plot :
s.rescale_path_length(100 * u("mm")).plot(nfig="same")

import matplotlib.pyplot as plt

plt.title(s.c["molecule"])

Fix #628

---

Note @HajimeKawahara the cross-section parsing is added directly in the API (hitranapi)

[erwanp]

@EkulRF have a look and confirm this is what you need; then we'll merge

[EkulRF]

Thanks @erwanp

I get the following error when I have the relevant xsc files saved to a local directory:

datafile = getTestFile(filepath)

Exception has occurred: FileNotFoundError Test file ~/CH3COCH3_297.8_700.0_700.0-1780.0_13.xsc` does not exist. Choose one of:

• hitran_co2_626_bandhead_4165_4200nm.par
• geisa_CO2_fragment.par
• co2_cdsd_hamiltonian_fragment.levels
• geisa_CO_fragment.par
• N2C_specair_380nm.spec
• synth-NH3-1-500-2000cm-P10-mf0.01-p1.spec
• cdsd_hitemp_09_header.txt
• CO2_measured_spectrum_4-5um.spec
• geisa_H2O_fragment.par
• hitran_co_3iso_2000_2300cm.par
• hitran_CO_fragment.par
• CO_Tgas1500K_mole_fraction0.01.spec
• Corentin_0_100cm_DownSampled_20cm_10pctCO2_1-wc-gw450-gr300-sl1500-acc5000-.spec
• CO_Tgas1500K_mole_fraction0.5.spec
• CO2abscoeff_300K_4150_4400nm.txt
• geisa_O2_fragment.par
• hitran_2016_H2O_2iso_2000_2100cm.par
• cdsd_hitemp_09_fragment.txt
• calc_N2C_spectrum_Trot1200_Tvib3000.txt
• hitran_CO2_fragment.par
• slitfunction.txt
• calc_N2C_spectrum_Trot1200_Tvib3000_slit0.1.txt or use force=True`

The file is correctly pathed, etc. Am I missing something or have I stored the .xsc file incorrectly?

[minouHub]

@erwanp any update on this one?