Optical constants

Refractive index of CsI (Cesium iodide)

Li 1976: n 0.25–67 µm

Data: formula 1
Range: 0.25–67 µm
Licence: CC0-1.0

Axis Log x Log y

Click the plot to set the calculator wavelength.

At one wavelength

Refractive index n: 1.78756
Extinction coefficient k: 0

Permittivity ε₁: 3.19538
Permittivity ε₂: 0

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

Abbe number V_d: 24.018
Chromatic dispersion dn/dλ: -0.164948 µm⁻¹

Group index n_g: 1.88449
Group velocity dispersion: 340.111 fs²/mm

Dispersion parameter D: -1855.49 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

# CsI (Cesium iodide): Li 1976: n 0.25–67 µm
csi = ls.fetch_refractiveindex("main", "CsI", "Li", ref="c5c2f188e848453def5970e347399d653df2ffc2")
print(csi.range_nm)  # (250, 67000) nm
eps = csi.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_3cad050bd641/lightsmith"
csi = ls.Tabulated.model_validate(json.load(urllib.request.urlopen(url)))
print(csi.source)  # citation and provenance travel with the data

Any dataset here, as the library's Tabulated material (csi/li-1976).

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

import json, urllib.request
import lightsmith as ls

url = "https://materials.lightsmith.dev/v1/datasets/ds_3cad050bd641/lightsmith?model=drude_lorentz"
csi_dl = ls.DrudeLorentz.model_validate(json.load(urllib.request.urlopen(url)))

A dispersive Drude–Lorentz model for time-domain solvers.

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.

Dispersion formula

Sellmeier (formula 1), λ in µm

n^{2} - 1 = 0.27587 + \frac{0.68689 λ^{2}}{λ^{2} - {0.13}^{2}} + \frac{0.2609 λ^{2}}{λ^{2} - {0.147}^{2}} + \frac{0.06256 λ^{2}}{λ^{2} - {0.163}^{2}} + \frac{0.06527 λ^{2}}{λ^{2} - {0.177}^{2}} + \frac{0.14991 λ^{2}}{λ^{2} - {0.185}^{2}} + \frac{0.51818 λ^{2}}{λ^{2} - {0.206}^{2}} + \frac{0.01918 λ^{2}}{λ^{2} - {0.218}^{2}} + \frac{3.38229 λ^{2}}{λ^{2} - {161.29}^{2}}

Valid from 0.25 to 67.0 µm.

Coefficients as stored

C_i	Value
C1	0.27587
C2	0.68689
C3	0.13
C4	0.2609
C5	0.147
C6	0.06256
C7	0.163
C8	0.06527
C9	0.177
C10	0.14991
C11	0.185
C12	0.51818
C13	0.206
C14	0.01918
C15	0.218
C16	3.38229
C17	161.29

Comments and conditions

297 K (24 °C).

References

H. H. Li. Refractive index of alkali halides and its wavelength and temperature derivatives. J. Phys. Chem. Ref. Data 5, 329-528 (1976) and references therein.
* Sellmeier formula is derived by fitting experimental data from several sources.

doi:10.1063/1.555536 Refractive index of alkali halides and its wavelength and temperature derivatives, Journal of Physical and Chemical Reference Data (1976)

Cite

H. H. Li. Refractive index of alkali halides and its wavelength and temperature derivatives. Journal of Physical and Chemical Reference Data, 5, 329-528 (1976), doi:10.1063/1.555536; Data from the refractiveindex.info database (M. N. Polyanskiy, Sci. Data 11, 94 (2024), doi:10.1038/s41597-023-02898-2)

Data

Computed on 400 wavelengths, the same grid as the API and the library

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

CsI (Cesium iodide), Li 1976: n 0.25–67 µm: n and k versus wavelength
λ (µm)	n
0.25	2.209377
0.253528	2.180373
0.257105	2.154381
0.260733	2.130923
0.264413	2.109621
0.268144	2.090176
0.271928	2.072342
0.275765	2.055917
0.279656	2.040734
0.283602	2.026653
0.287604	2.013554
0.291663	2.001337
0.295779	1.989914
0.299952	1.979209
0.304185	1.969157
0.308477	1.9597
0.31283	1.950787
0.317245	1.942374
0.321721	1.93442
0.326261	1.926891
0.330865	1.919754
0.335534	1.91298
0.340269	1.906545
0.34507	1.900424
0.34994	1.894598
0.354878	1.889045
0.359885	1.88375
0.364964	1.878695
0.370114	1.873867
0.375337	1.869251
0.380633	1.864835
0.386004	1.860608
0.391451	1.85656
0.396975	1.85268
0.402577	1.848959
0.408258	1.845389
0.414019	1.841963
0.419861	1.838672
0.425786	1.835509
0.431794	1.83247
0.437887	1.829547
0.444066	1.826735
0.450332	1.824028
0.456687	1.821423
0.463131	1.818914
0.469667	1.816496
0.476294	1.814166
0.483015	1.81192
0.489831	1.809754
0.496743	1.807665
0.503753	1.80565
0.510861	1.803704
0.51807	1.801826
0.525381	1.800013
0.532795	1.798262
0.540313	1.79657
0.547937	1.794936
0.555669	1.793356
0.56351	1.79183
0.571462	1.790354
0.579526	1.788926
0.587704	1.787546
0.595997	1.786211
0.604407	1.784919
0.612936	1.783669
0.621585	1.782459
0.630357	1.781288
0.639252	1.780154
0.648272	1.779057
0.65742	1.777994
0.666697	1.776965
0.676105	1.775968
0.685646	1.775003
0.695321	1.774067
0.705133	1.773161
0.715083	1.772283
0.725173	1.771431
0.735406	1.770606
0.745784	1.769807
0.756308	1.769032
0.76698	1.76828
0.777803	1.767551
0.788779	1.766845
0.799909	1.766159
0.811197	1.765495
0.822644	1.76485
0.834252	1.764225
0.846024	1.763618
0.857963	1.76303
0.87007	1.762459
0.882347	1.761905
0.894798	1.761367
0.907425	1.760846
0.92023	1.760339
0.933215	1.759848
0.946384	1.759371
0.959738	1.758908
0.973281	1.758459
0.987016	1.758022
1.00094	1.757599
1.01507	1.757188
1.02939	1.756788
1.04392	1.756401
1.05865	1.756024
1.07359	1.755658
1.08874	1.755303
1.1041	1.754958
1.11968	1.754624
1.13548	1.754298
1.1515	1.753982
1.16775	1.753675
1.18423	1.753377
1.20094	1.753087
1.21789	1.752806
1.23507	1.752532
1.2525	1.752266
1.27018	1.752008
1.2881	1.751757
1.30628	1.751513
1.32471	1.751276
1.3434	1.751046
1.36236	1.750822
1.38158	1.750605
1.40108	1.750393
1.42085	1.750187
1.4409	1.749988
1.46123	1.749793
1.48185	1.749604
1.50276	1.74942
1.52397	1.749242
1.54547	1.749068
1.56728	1.748899
1.5894	1.748735
1.61183	1.748575
1.63457	1.748419
1.65764	1.748268
1.68103	1.748121
1.70475	1.747978
1.72881	1.747839
1.7532	1.747703
1.77794	1.747571
1.80303	1.747443
1.82847	1.747318
1.85427	1.747196
1.88044	1.747078
1.90697	1.746962
1.93388	1.74685
1.96117	1.746741
1.98885	1.746634
2.01691	1.746531
2.04537	1.746429
2.07424	1.746331
2.10351	1.746235
2.13319	1.746141
2.16329	1.74605
2.19382	1.745961
2.22477	1.745875
2.25617	1.74579
2.28801	1.745707
2.32029	1.745627
2.35303	1.745548
2.38624	1.745472
2.41991	1.745397
2.45406	1.745324
2.48869	1.745252
2.52381	1.745182
2.55942	1.745114
2.59554	1.745047
2.63216	1.744982
2.6693	1.744918
2.70697	1.744856
2.74517	1.744795
2.78391	1.744735
2.82319	1.744676
2.86303	1.744618
2.90343	1.744562
2.9444	1.744507
2.98595	1.744452
3.02809	1.744399
3.07081	1.744347
3.11415	1.744295
3.15809	1.744245
3.20266	1.744195
3.24785	1.744146
3.29368	1.744098
3.34016	1.744051
3.38729	1.744004
3.43509	1.743958
3.48356	1.743912
3.53272	1.743867
3.58257	1.743822
3.63312	1.743778
3.68439	1.743735
3.73638	1.743692
3.78911	1.743649
3.84258	1.743607
3.8968	1.743565
3.95179	1.743523
4.00755	1.743481
4.0641	1.74344
4.12145	1.743399
4.17961	1.743358
4.23859	1.743317
4.2984	1.743276
4.35906	1.743236
4.42057	1.743195
4.48295	1.743154
4.54621	1.743113
4.61036	1.743073
4.67541	1.743032
4.74139	1.742991
4.8083	1.74295
4.87615	1.742908
4.94495	1.742867
5.01473	1.742825
5.0855	1.742782
5.15726	1.74274
5.23003	1.742697
5.30384	1.742654
5.37868	1.74261
5.45458	1.742566
5.53155	1.742521
5.60961	1.742476
5.68876	1.74243
5.76904	1.742384
5.85045	1.742337
5.933	1.742289
6.01672	1.74224
6.10163	1.742191
6.18773	1.742141
6.27504	1.74209
6.36359	1.742038
6.45339	1.741986
6.54445	1.741932
6.6368	1.741877
6.73046	1.741822
6.82543	1.741765
6.92174	1.741707
7.01942	1.741648
7.11847	1.741587
7.21892	1.741526
7.32079	1.741463
7.42409	1.741398
7.52885	1.741332
7.63509	1.741265
7.74283	1.741196
7.85209	1.741126
7.9629	1.741054
8.07526	1.74098
8.18921	1.740905
8.30477	1.740827
8.42196	1.740748
8.54081	1.740667
8.66133	1.740584
8.78355	1.740498
8.90749	1.740411
9.03319	1.740321
9.16066	1.740229
9.28992	1.740135
9.42101	1.740038
9.55396	1.739939
9.68877	1.739837
9.82549	1.739732
9.96414	1.739625
10.1047	1.739515
10.2473	1.739402
10.3919	1.739286
10.5386	1.739166
10.6873	1.739044
10.8381	1.738918
10.991	1.738789
11.1461	1.738656
11.3034	1.738519
11.4629	1.738379
11.6247	1.738235
11.7887	1.738087
11.9551	1.737935
12.1238	1.737779
12.2948	1.737618
12.4683	1.737453
12.6443	1.737283
12.8227	1.737108
13.0037	1.736929
13.1871	1.736744
13.3732	1.736554
13.5619	1.736359
13.7533	1.736158
13.9474	1.735952
14.1442	1.73574
14.3438	1.735521
14.5462	1.735297
14.7515	1.735066
14.9596	1.734829
15.1707	1.734584
15.3848	1.734333
15.6019	1.734074
15.8221	1.733808
16.0453	1.733535
16.2717	1.733253
16.5014	1.732964
16.7342	1.732666
16.9704	1.732359
17.2098	1.732043
17.4527	1.731719
17.6989	1.731384
17.9487	1.731041
18.202	1.730687
18.4588	1.730322
18.7193	1.729948
18.9835	1.729562
19.2513	1.729165
19.523	1.728756
19.7985	1.728335
20.0779	1.727902
20.3612	1.727456
20.6485	1.726997
20.9399	1.726524
21.2354	1.726037
21.535	1.725536
21.8389	1.72502
22.1471	1.724489
22.4596	1.723942
22.7765	1.723379
23.0979	1.722798
23.4239	1.722201
23.7544	1.721585
24.0896	1.720951
24.4295	1.720298
24.7743	1.719626
25.1239	1.718933
25.4784	1.718219
25.8379	1.717483
26.2025	1.716726
26.5723	1.715945
26.9472	1.71514
27.3275	1.714311
27.7131	1.713456
28.1042	1.712575
28.5007	1.711667
28.9029	1.710732
29.3108	1.709767
29.7244	1.708772
30.1438	1.707747
30.5692	1.706689
31.0006	1.705599
31.438	1.704475
31.8816	1.703315
32.3315	1.702119
32.7878	1.700885
33.2504	1.699612
33.7196	1.698298
34.1955	1.696943
34.678	1.695544
35.1673	1.694101
35.6636	1.692611
36.1668	1.691073
36.6772	1.689485
37.1948	1.687845
37.7196	1.686152
38.2519	1.684404
38.7917	1.682597
39.3391	1.680731
39.8942	1.678803
40.4571	1.676811
41.028	1.674752
41.607	1.672623
42.1941	1.670422
42.7895	1.668146
43.3933	1.665793
44.0056	1.663358
44.6266	1.66084
45.2563	1.658233
45.895	1.655535
46.5426	1.652743
47.1994	1.649851
47.8654	1.646856
48.5408	1.643754
49.2258	1.640539
49.9204	1.637207
50.6249	1.633753
51.3392	1.630172
52.0637	1.626457
52.7984	1.622602
53.5434	1.618601
54.299	1.614448
55.0652	1.610134
55.8422	1.605653
56.6302	1.600996
57.4293	1.596154
58.2397	1.591119
59.0616	1.585879
59.895	1.580426
60.7402	1.574747
61.5973	1.56883
62.4665	1.562664
63.348	1.556232
64.2419	1.549522
65.1484	1.542517
66.0677	1.5352
67	1.527552

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: —

CsI (Cesium iodide): all datasets

About CsI (Cesium iodide)

Caesium iodide (CsI) is an inorganic compound known for its wide range of applications, from scintillation counters in high-energy physics to the field of medical imaging. This compound forms colorless, water-soluble crystals and has high gamma-ray stopping power, making it particularly useful as a scintillator material. It is also notable for its transparency in the wide spectral range from ultraviolet to long-wavelength infrared, which makes it valuable in infrared optics. In addition, CsI is often used in mass spectrometry as a matrix to help ionize samples. Like other caesium compounds, CsI should be handled with care due to its reactivity and potential health risks associated with iodine and caesium, such as thyroid gland issues and cellular ion channel disruptions. As a result, strict safety protocols are essential for its handling and storage. Overall, CsI is a highly versatile material with a plethora of applications in both scientific research and industrial processes.

Caesium iodide - Wikipedia

More about CsI (Cesium iodide) →

Provenance

Version: 1 (snapshot c5c2f18)
Source page: refractiveindex.info
Original file: database/data/main/CsI/nk/Li.yml
ID: ds_3cad050bd641
API: /v1/datasets/ds_3cad050bd641

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