Optical constants

Refractive index of Cs (Caesium)

Whang et al. 1971: n,k 0.129–0.344 µm

Data: tabulated nk
Range: 0.1294–0.3444 µm
Points: 29
Licence: CC0-1.0

Axis Log x Log y

Click the plot to set the calculator wavelength.

At one wavelength

Refractive index n: 0.962506
Extinction coefficient k: 0.114114

Permittivity ε₁: 0.913396
Permittivity ε₂: 0.219671

Absorption coefficient α: 67962 cm⁻¹
Penetration depth δ = λ/(2πk): 294.282 nm

Abbe number V_d: —
Chromatic dispersion dn/dλ: -1.01266 µm⁻¹

Group index n_g: 1.17618
Group velocity dispersion: — fs²/mm

Dispersion parameter D: — ps/(nm·km)
Photon energy: 5.87603 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

# Cs (Caesium): Whang et al. 1971: n,k 0.129–0.344 µm
cs = ls.fetch_refractiveindex("main", "Cs", "Whang", ref="c5c2f188e848453def5970e347399d653df2ffc2")
print(cs.range_nm)  # (129.4, 344.4) nm
eps = cs.eps([211])  # 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_f39b4703bf1e/lightsmith"
cs = ls.Tabulated.model_validate(json.load(urllib.request.urlopen(url)))
print(cs.source)  # citation and provenance travel with the data

Any dataset here, as the library's Tabulated material (cs/whang-1971).

# ... load cs as above, then:
sim = ls.Simulation(
    particles=[ls.Particle(shape=ls.Sphere(radius_nm=50), material=cs)],
    medium_index=1.0,
    wavelengths=ls.WavelengthRange(start_nm=130, stop_nm=344, 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.

References

U. S. Whang, E. T. Arakawa, T. A. Callcott. Optical properties of Cs for photons of energy 3.6–9.6 eV. J. Opt. Soc. Am. 61, 740-745 (1971)

doi:10.1364/josa.61.000740 Optical Properties of Cs for Photons of Energy 36–96 eV*, Journal of the Optical Society of America (1971)

Cite

U. S. Whang, E. T. Arakawa and T. A. Callcott. Optical Properties of Cs for Photons of Energy 36–96 eV*. Journal of the Optical Society of America, 61, 740 (1971), doi:10.1364/josa.61.000740; Data from the refractiveindex.info database (M. N. Polyanskiy, Sci. Data 11, 94 (2024), doi:10.1038/s41597-023-02898-2)

Data

29 rows as published

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

Cs (Caesium), Whang et al. 1971: n,k 0.129–0.344 µm: n and k versus wavelength
λ (µm)	n	k
0.1294	1.11	0.02
0.1372	1.09	0.025
0.1418	1.08	0.028
0.1477	1.07	0.032
0.1536	1.05	0.036
0.1597	1.04	0.041
0.1625	1.03	0.046
0.1687	1.02	0.055
0.175	1.0	0.064
0.1817	0.995	0.072
0.1862	0.99	0.079
0.1897	0.986	0.084
0.1963	0.979	0.093
0.2036	0.97	0.101
0.2115	0.962	0.115
0.2135	0.96	0.117
0.2166	0.957	0.122
0.226	0.947	0.135
0.2282	0.945	0.138
0.2296	0.943	0.14
0.2377	0.935	0.147
0.248	0.924	0.153
0.2583	0.913	0.157
0.2696	0.9	0.159
0.282	0.888	0.162
0.2952	0.874	0.164
0.31	0.85	0.169
0.3263	0.785	0.191
0.3444	0.715	0.224

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: —

Cs (Caesium): all datasets

About Cs (Caesium)

Caesium (Cs) is an alkali metal characterised by its softness and extremely low melting point for a metal, just above room temperature at 28.5 °C (83.3 °F). It is silvery-gold in colour and highly reactive, especially with water, leading to its storage in mineral oil or inert gases. In the realm of technology, caesium is crucial for the operation of atomic clocks, which use the microwave spectral line emitted by electrons in caesium atoms to define the second, the base unit of time. Due to the high precision of caesium-based atomic clocks, they serve as the timekeeping standard for global navigation satellite systems like GPS. Caesium is also used in photoelectric cells, ion propulsion systems, and as a catalyst in certain organic reactions. Despite its technological utility, caesium compounds must be handled with care as they can be corrosive and pose health risks upon exposure. Overall, caesium is a fascinating element whose unique properties make it indispensable in precision timekeeping and various specialised applications.

More about Cs (Caesium) →

Provenance

Version: 1 (snapshot c5c2f18)
Source page: refractiveindex.info
Original file: database/data/main/Cs/nk/Whang.yml
ID: ds_f39b4703bf1e
API: /v1/datasets/ds_f39b4703bf1e

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