Refractive index of (C₃₇H₂₄O₆N₂)_n (Polyetherimide, PEI)

import lightsmith as ls

# (C37H24O6N2)n (Polyetherimide, PEI): Zhang et al. 2020: n,k 0.4–20 µm
polyetherimide = ls.fetch_refractiveindex("organic", "polyetherimide", "Zhang", ref="c5c2f188e848453def5970e347399d653df2ffc2")
print(polyetherimide.range_nm)  # (400, 19942) nm
eps = polyetherimide.eps([633])  # complex permittivity

import json, urllib.request
import lightsmith as ls

url = "https://materials.lightsmith.dev/v1/datasets/ds_781b373947d7/lightsmith"
polyetherimide = ls.Tabulated.model_validate(json.load(urllib.request.urlopen(url)))
print(polyetherimide.source)  # citation and provenance travel with the data

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