Refractive index of CH₄ (Methane)

import lightsmith as ls

# CH4 (Methane): Martonchik and Orton 1994: Liquid at 90 K; n,k 0.002–71.4 µm
ch4 = ls.fetch_refractiveindex("organic", "methane", "Martonchik-liquid-90K", ref="c5c2f188e848453def5970e347399d653df2ffc2")
print(ch4.range_nm)  # (2, 71430) nm
eps = ch4.eps([633])  # complex permittivity

import json, urllib.request
import lightsmith as ls

url = "https://materials.lightsmith.dev/v1/datasets/ds_5909a303586c/lightsmith"
ch4 = ls.Tabulated.model_validate(json.load(urllib.request.urlopen(url)))
print(ch4.source)  # citation and provenance travel with the data

# ... load ch4 as above, then:
sim = ls.Simulation(
    particles=[ls.Particle(shape=ls.Sphere(radius_nm=50), material=ch4)],
    medium_index=1.0,
    wavelengths=ls.WavelengthRange(start_nm=400, stop_nm=1000, num=81),
)
res = ls.solve(sim)  # exact Mie for a sphere
print(res.q_ext)     # extinction efficiency at each wavelength