Refractive index of Cr (Chromium)

import lightsmith as ls

# Cr (Chromium): Rakić et al. 1998: Brendel-Bormann model; n,k 0.248–62.0 µm
cr = ls.fetch_refractiveindex("main", "Cr", "Rakic-BB", ref="c5c2f188e848453def5970e347399d653df2ffc2")
print(cr.range_nm)  # (247.97, 61992) nm
eps = cr.eps([633])  # complex permittivity

import json, urllib.request
import lightsmith as ls

url = "https://materials.lightsmith.dev/v1/datasets/ds_46e3b10e7354/lightsmith"
cr = ls.Tabulated.model_validate(json.load(urllib.request.urlopen(url)))
print(cr.source)  # citation and provenance travel with the data

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