Refractive index of Au (Gold)

import lightsmith as ls

# Au (Gold): Rakić et al. 1998: Brendel-Bormann model; n,k 0.248–6.20 µm
au = ls.fetch_refractiveindex("main", "Au", "Rakic-BB", ref="c5c2f188e848453def5970e347399d653df2ffc2")
print(au.range_nm)  # (247.97, 6199.2) nm
eps = au.eps([633])  # complex permittivity

import json, urllib.request
import lightsmith as ls

url = "https://materials.lightsmith.dev/v1/datasets/ds_ab02da0042e2/lightsmith"
au = ls.Tabulated.model_validate(json.load(urllib.request.urlopen(url)))
print(au.source)  # citation and provenance travel with the data

# ... load au as above, then:
sim = ls.Simulation(
    particles=[ls.Particle(shape=ls.Sphere(radius_nm=50), material=au)],
    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