Optical constants
Refractive index of CH4 (Methane)
Rollefson and Havens 1940: Gas at 0 °C; n 1.68–14.8 µm
- Data
- tabulated n
- Range
- 1.68–14.8 µm
- Points
- 49
- Temperature
- 273.15 K
- State
- gas
- Licence
- CC0-1.0
Plot
Click the plot to set the calculator wavelength.
At one wavelength
- Refractive index n
- 1.00044
- Extinction coefficient k
- 0
- Permittivity ε1
- 1.00087
- Permittivity ε2
- 0
- Absorption coefficient α
- 0 cm⁻¹
- Penetration depth δ = λ/(2πk)
- — nm
- Abbe number Vd
- —
- Chromatic dispersion dn/dλ
- -2.77778e-06 µm⁻¹
- Group index ng
- 1.00045
- Group velocity dispersion
- — fs²/mm
- Dispersion parameter D
- — ps/(nm·km)
- Photon energy
- 0.248465 eV
ε = (n + ik)², α = 4πk/λ, ng = n − λ dn/dλ, GVD = λ³/(2πc²) d²n/dλ², D = −(λ/c) d²n/dλ². Group-velocity dispersion is given for formula data only.
Use it in Lightsmith
Load this data in Python, simulate in one more line
pip install lightsmith
import lightsmith as ls
# CH4 (Methane): Rollefson and Havens 1940: Gas at 0 °C; n 1.68–14.8 µm
ch4 = ls.fetch_refractiveindex("organic", "methane", "Rollefson", ref="c5c2f188e848453def5970e347399d653df2ffc2")
print(ch4.range_nm) # (1680, 14800) nm
eps = ch4.eps([4990]) # complex permittivityDownloads the original record once (pinned to the imported snapshot) and caches it.
import json, urllib.request
import lightsmith as ls
url = "https://materials.lightsmith.dev/v1/datasets/ds_0294be54ca49/lightsmith"
ch4 = ls.Tabulated.model_validate(json.load(urllib.request.urlopen(url)))
print(ch4.source) # citation and provenance travel with the dataAny dataset here, as the library's Tabulated material (methane/rollefson-havens-1940).
# ... 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=1680, stop_nm=14800, num=81),
)
res = ls.solve(sim) # exact Mie for a sphere
print(res.q_ext) # extinction efficiency at each wavelengthSame spec runs with DDA, FDTD, BEM or T-matrix: ls.compare(sim, ["mie", "dda"]).
Lightsmith is open source (MIT): Mie, T-matrix, BEM, DDA, FDTD, RCWA, TMM, mode solvers and inverse design behind one spec, on CPU or GPU. GitHub.
Comments and conditions
Conditions
- temperature
- 273.15 K
- pressure
- 101325
References
- doi:10.1103/physrev.57.710 Index of Refraction of Methane in the Infra-Red and the Dipole Moment of the CH Bond, Physical Review (1940)
Cite
R. Rollefson and R. Havens. Index of Refraction of Methane in the Infra-Red and the Dipole Moment of the CH Bond. Physical Review, 57, 710-717 (1940), doi:10.1103/physrev.57.710; Data from the refractiveindex.info database (M. N. Polyanskiy, Sci. Data 11, 94 (2024), doi:10.1038/s41597-023-02898-2)
Data
49 rows as published| λ (µm) | n |
|---|---|
| 1.68 | 1.0004365 |
| 1.94 | 1.0004357 |
| 2.67 | 1.0004327 |
| 2.79 | 1.0004315 |
| 2.96 | 1.0004278 |
| 3.0 | 1.00042585 |
| 3.64 | 1.00044525 |
| 3.75 | 1.0004428 |
| 3.9 | 1.0004411 |
| 4.04 | 1.0004401 |
| 4.45 | 1.0004378 |
| 4.57 | 1.0004373 |
| 4.7 | 1.0004368 |
| 5.06 | 1.0004358 |
| 5.4 | 1.00043455 |
| 5.6 | 1.000434 |
| 5.84 | 1.0004326 |
| 5.98 | 1.00043205 |
| 6.33 | 1.00042905 |
| 6.56 | 1.0004263 |
| 6.79 | 1.0004218 |
| 6.94 | 1.0004168 |
| 7.0 | 1.0004136 |
| 8.36 | 1.0004665 |
| 8.42 | 1.0004636 |
| 8.48 | 1.000462 |
| 8.57 | 1.0004603 |
| 8.63 | 1.000459 |
| 8.7 | 1.0004577 |
| 8.8 | 1.000456 |
| 8.89 | 1.0004547 |
| 8.95 | 1.0004538 |
| 9.05 | 1.0004534 |
| 9.2 | 1.0004522 |
| 9.41 | 1.0004509 |
| 9.52 | 1.0004506 |
| 9.73 | 1.0004496 |
| 10.11 | 1.0004486 |
| 10.28 | 1.0004476 |
| 10.38 | 1.0004477 |
| 10.8 | 1.0004465 |
| 10.94 | 1.0004467 |
| 11.46 | 1.0004471 |
| 11.89 | 1.0004453 |
| 12.36 | 1.0004458 |
| 13.2 | 1.000445 |
| 13.6 | 1.0004437 |
| 14.0 | 1.0004484 |
| 14.8 | 1.0004438 |
Optical transmission calculator
Free-standing sample in vacuum, normal incidence- Transmittance T
- —
- Reflectance R
- —
Fresnel reflection calculator
- Rp
- —
- Rs
- —
- R = (Rp+Rs)/2
- —
- Phase φp
- —
- Phase φs
- —
- Brewster angle θB
- —
- Critical angle θC
- —
Gaseous methane at standard conditions. 0 °C, 760 torr (101.325 kPa).