Optical constants

Refractive index of Cs (Caesium)

Smith 1970: n,k 0.313–2.42 µm

Data: tabulated nk
Range: 0.3125–2.422 µm
Points: 30
Licence: CC0-1.0

Axis Log x Log y

Click the plot to set the calculator wavelength.

At one wavelength

Refractive index n: 0.261508
Extinction coefficient k: 1.0829

Permittivity ε₁: -1.1043
Permittivity ε₂: 0.566376

Absorption coefficient α: 231589 cm⁻¹
Penetration depth δ = λ/(2πk): 86.3598 nm

Abbe number V_d: —
Chromatic dispersion dn/dλ: -0.0358953 µm⁻¹

Group index n_g: 0.2826
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

# Cs (Caesium): Smith 1970: n,k 0.313–2.42 µm
cs = ls.fetch_refractiveindex("main", "Cs", "Smith", ref="c5c2f188e848453def5970e347399d653df2ffc2")
print(cs.range_nm)  # (312.539, 2421.57) nm
eps = cs.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_1d76d964520a/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/smith-1970).

# ... 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=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.

References

N. V. Smith. Optical constants of rubidium and cesium from 0.5 to 4.0 eV. Phs. Rev. B 2, 2840-2848 (1970)

doi:10.1103/physrevb.2.2840 Optical Constants of Rubidium and Cesium from 0.5 to 4.0 eV, Physical Review B (1970)

Cite

Neville V. Smith. Optical Constants of Rubidium and Cesium from 0.5 to 4.0 eV. Physical Review B, 2, 2840-2848 (1970), doi:10.1103/physrevb.2.2840; Data from the refractiveindex.info database (M. N. Polyanskiy, Sci. Data 11, 94 (2024), doi:10.1038/s41597-023-02898-2)

Data

30 rows as published

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

Cs (Caesium), Smith 1970: n,k 0.313–2.42 µm: n and k versus wavelength
λ (µm)	n	k
0.312539	0.828383	0.173833
0.334099	0.690892	0.224348
0.364981	0.595515	0.269515
0.369992	0.562034	0.299804
0.386967	0.508871	0.333091
0.399949	0.441436	0.399832
0.420001	0.400244	0.45847
0.439972	0.339727	0.569574
0.469993	0.302976	0.683223
0.512967	0.272621	0.852832
0.556982	0.262607	0.984359
0.609858	0.260709	1.154543
0.673096	0.266029	1.362634
0.76298	0.279706	1.651737
0.885601	0.3026	1.982818
1.017098	0.318736	2.356182
1.185317	0.316566	2.751402
1.343274	0.306142	3.139064
1.435002	0.298357	3.408668
1.515699	0.288149	3.564131
1.595678	0.279656	3.770704
1.689158	0.272608	4.016754
1.766157	0.264679	4.188085
1.836803	0.257275	4.337763
1.904519	0.250691	4.54344
1.980578	0.238743	4.695423
2.039214	0.246495	4.862176
2.112167	0.241092	5.041639
2.167556	0.243133	5.153554
2.421566	0.262612	5.896521

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/Smith.yml
ID: ds_1d76d964520a
API: /v1/datasets/ds_1d76d964520a

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