Optical constants

Refractive index of CH₄ (Methane)

Martonchik and Orton 1994: Solid at 90 K; n,k 0.002–100 µm

Data: tabulated nk
Range: 0.002–100 µm
Points: 41
Temperature: 90 K
State: solid
Licence: CC0-1.0

Axis Log x Log y

Click the plot to set the calculator wavelength.

At one wavelength

Refractive index n: 1.32194
Extinction coefficient k: 0

Permittivity ε₁: 1.74751
Permittivity ε₂: 0

Absorption coefficient α: 0 cm⁻¹
Penetration depth δ = λ/(2πk): — nm

Abbe number V_d: —
Chromatic dispersion dn/dλ: -0.0216667 µm⁻¹

Group index n_g: 1.33467
Group velocity dispersion: — fs²/mm

Dispersion parameter D: — ps/(nm·km)
Photon energy: 2.11001 eV

ε = (n + ik)², α = 4πk/λ, n_g = 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): Martonchik and Orton 1994: Solid at 90 K; n,k 0.002–100 µm
ch4 = ls.fetch_refractiveindex("organic", "methane", "Martonchik-solid-90K", ref="c5c2f188e848453def5970e347399d653df2ffc2")
print(ch4.range_nm)  # (2, 100000) nm
eps = ch4.eps([633])  # complex permittivity

Downloads 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_2acfee1698c9/lightsmith"
ch4 = ls.Tabulated.model_validate(json.load(urllib.request.urlopen(url)))
print(ch4.source)  # citation and provenance travel with the data

Any dataset here, as the library's Tabulated material (methane/martonchik-orton-1994-solid-90k).

# ... 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

Same spec runs with DDA, FDTD, BEM or T-matrix: ls.compare(sim, ["mie", "dda"]).

Materials guide Open a sphere of it in Studio Quick start Ask the community

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

Phase I solid methane at 90 K (-183.15 °C, melting point)
CAUTION: don't rely on interpolated values: Most data points represent values at local maxima or minima

Conditions

temperature: 90 K

References

J. V. Martonchik and G. S. Orton. Optical constants of liquid and solid methane. Appl. Opt. 33, 8306-8317 (1994)

doi:10.1364/ao.33.008306 Optical constants of liquid and solid methane, Applied Optics (1994)

Cite

John V. Martonchik and Glenn S. Orton. Optical constants of liquid and solid methane. Applied Optics, 33, 8306 (1994), doi:10.1364/ao.33.008306; Data from the refractiveindex.info database (M. N. Polyanskiy, Sci. Data 11, 94 (2024), doi:10.1038/s41597-023-02898-2)

Data

41 rows as published

CSV comma separated TXT tab separated YAML n, k Full database record original YAML All quantities CSV JSON metadata

CH4 (Methane), Martonchik and Orton 1994: Solid at 90 K; n,k 0.002–100 µm: n and k versus wavelength
λ (µm)	n	k
0.002	0.971	0.0
0.0114	0.993	0.002607
0.0545	0.842	0.2332
0.09	1.228	0.7096
0.0987	1.491	0.5681
0.1012	1.486	0.5203
0.1087	1.554	0.4104
0.1162	1.515	0.3518
0.12	1.53	0.3632
0.1337	1.767	0.1981
0.4	1.326	0.0
1.0	1.313	0.0
1.138	1.313	1.9e-05
1.165	1.313	4.577e-05
1.336	1.312	5.023e-05
1.371	1.312	1.828e-05
1.385	1.312	9.073e-06
1.402	1.312	3.642e-05
1.412	1.312	2.368e-05
1.669	1.311	0.0004737
1.724	1.311	0.0002446
1.785	1.311	8.213e-05
1.796	1.311	0.0001807
2.317	1.307	0.003453
2.324	1.31	0.006189
2.329	1.314	0.003096
2.377	1.306	0.005058
2.379	1.312	0.009199
2.381	1.316	0.005547
3.315	1.19	0.1312
3.322	1.339	0.2564
3.33	1.451	0.1107
3.534	1.318	0.002877
3.546	1.319	0.004574
3.565	1.321	0.00257
7.675	0.81	0.4585
7.692	1.265	0.9598
7.71	1.845	0.5199
36.36	1.316	0.0007624
62.5	1.317	0.002636
100.0	1.318	0.002387

Optical transmission calculator

Free-standing sample in vacuum, normal incidence

Transmittance T: —
Reflectance R: —

Fresnel reflection calculator

R_p: —
R_s: —
R = (R_p+R_s)/2: —
Phase φ_p: —
Phase φ_s: —
Brewster angle θ_B: —
Critical angle θ_C: —

CH₄ (Methane): all datasets

Gas

Liquid

Solid

About CH4 (Methane)

Methane (CH₄) is the simplest alkane and is a colorless, odorless gas under standard conditions. It is the primary constituent of natural gas and is notable for being a potent greenhouse gas. In the environment, methane is produced during the anaerobic decomposition of organic matter, such as in wetlands, ruminant digestion, and landfills. It can also be found in various industrial processes and is used as a fuel for heating and electricity generation. In the realm of optics, methane's refractive properties might be of interest, especially when considering its potential presence in gaseous atmospheres of extraterrestrial bodies.

More about CH4 (Methane) →

Provenance

Version: 1 (snapshot c5c2f18)
Source page: refractiveindex.info
Original file: database/data/organic/CH4 - methane/nk/Martonchik-solid-90K.yml
ID: ds_2acfee1698c9
API: /v1/datasets/ds_2acfee1698c9

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