Optical constants

Refractive index of LiI (Lithium iodide)

Li 1976: n 0.25–25 µm

Data: formula 1
Range: 0.25–25 µm
Licence: CC0-1.0

Axis Log x Log y

Click the plot to set the calculator wavelength.

At one wavelength

Refractive index n: 1.95515
Extinction coefficient k: 0

Permittivity ε₁: 3.82263
Permittivity ε₂: 0

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

Abbe number V_d: 215.07
Chromatic dispersion dn/dλ: -0.0224355 µm⁻¹

Group index n_g: 1.96834
Group velocity dispersion: 44.9662 fs²/mm

Dispersion parameter D: -245.314 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

# LiI (Lithium iodide): Li 1976: n 0.25–25 µm
lii = ls.fetch_refractiveindex("main", "LiI", "Li", ref="c5c2f188e848453def5970e347399d653df2ffc2")
print(lii.range_nm)  # (250, 25000) nm
eps = lii.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_0d9d8474f4dc/lightsmith"
lii = ls.Tabulated.model_validate(json.load(urllib.request.urlopen(url)))
print(lii.source)  # citation and provenance travel with the data

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

# ... load lii as above, then:
sim = ls.Simulation(
    particles=[ls.Particle(shape=ls.Sphere(radius_nm=50), material=lii)],
    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_0d9d8474f4dc/lightsmith?model=drude_lorentz"
lii_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 = 2.55 + \frac{0.25 λ^{2}}{λ^{2} - {0.171}^{2}} + \frac{7.23 λ^{2}}{λ^{2} - {70.42}^{2}}

Valid from 0.25 to 25.0 µm.

Coefficients as stored

C_i	Value
C1	2.55
C2	0.25
C3	0.171
C4	7.23
C5	70.42

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 derivation is based on a single data point and knowledge of the dielectric constants and the characteristic absorption peaks.

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

LiI (Lithium iodide), Li 1976: n 0.25–25 µm: n and k versus wavelength
λ (µm)	n
0.25	2.004921
0.252902	2.002614
0.255838	2.000444
0.258808	1.998399
0.261812	1.996469
0.264852	1.994645
0.267926	1.992919
0.271036	1.991283
0.274183	1.989732
0.277366	1.988259
0.280586	1.986858
0.283843	1.985525
0.287138	1.984256
0.290471	1.983046
0.293843	1.981891
0.297254	1.980789
0.300705	1.979735
0.304196	1.978727
0.307727	1.977763
0.311299	1.976839
0.314913	1.975954
0.318569	1.975105
0.322267	1.97429
0.326008	1.973508
0.329792	1.972757
0.333621	1.972034
0.337494	1.97134
0.341412	1.970672
0.345375	1.970029
0.349384	1.969409
0.35344	1.968812
0.357543	1.968237
0.361694	1.967682
0.365893	1.967147
0.37014	1.966631
0.374437	1.966132
0.378784	1.965651
0.383181	1.965186
0.387629	1.964736
0.392129	1.964302
0.396681	1.963882
0.401286	1.963475
0.405944	1.963082
0.410657	1.962701
0.415424	1.962333
0.420246	1.961976
0.425125	1.96163
0.43006	1.961295
0.435052	1.96097
0.440103	1.960656
0.445212	1.96035
0.45038	1.960055
0.455608	1.959767
0.460897	1.959489
0.466248	1.959219
0.47166	1.958956
0.477136	1.958701
0.482674	1.958454
0.488278	1.958214
0.493946	1.95798
0.49968	1.957753
0.505481	1.957533
0.511348	1.957319
0.517285	1.95711
0.523289	1.956908
0.529364	1.956711
0.535509	1.956519
0.541726	1.956333
0.548015	1.956152
0.554376	1.955975
0.560812	1.955803
0.567322	1.955636
0.573908	1.955474
0.58057	1.955315
0.58731	1.955161
0.594128	1.95501
0.601025	1.954864
0.608002	1.954721
0.61506	1.954582
0.6222	1.954447
0.629423	1.954314
0.63673	1.954186
0.644121	1.95406
0.651599	1.953938
0.659163	1.953818
0.666815	1.953702
0.674556	1.953588
0.682386	1.953477
0.690308	1.953369
0.698321	1.953263
0.706428	1.95316
0.714629	1.953059
0.722924	1.95296
0.731317	1.952864
0.739806	1.95277
0.748394	1.952679
0.757082	1.952589
0.765871	1.952501
0.774762	1.952416
0.783756	1.952332
0.792854	1.95225
0.802058	1.95217
0.811369	1.952091
0.820788	1.952015
0.830316	1.951939
0.839955	1.951866
0.849705	1.951794
0.859569	1.951723
0.869548	1.951654
0.879642	1.951587
0.889853	1.95152
0.900183	1.951455
0.910633	1.951391
0.921204	1.951329
0.931898	1.951267
0.942717	1.951207
0.95366	1.951148
0.964731	1.95109
0.97593	1.951033
0.987259	1.950977
0.99872	1.950922
1.01031	1.950868
1.02204	1.950814
1.03391	1.950762
1.04591	1.95071
1.05805	1.95066
1.07033	1.95061
1.08276	1.95056
1.09533	1.950512
1.10804	1.950464
1.12091	1.950417
1.13392	1.95037
1.14708	1.950324
1.1604	1.950278
1.17387	1.950233
1.18749	1.950189
1.20128	1.950145
1.21523	1.950102
1.22933	1.950059
1.2436	1.950016
1.25804	1.949974
1.27264	1.949932
1.28742	1.94989
1.30236	1.949849
1.31748	1.949808
1.33278	1.949768
1.34825	1.949727
1.3639	1.949687
1.37973	1.949647
1.39575	1.949607
1.41195	1.949568
1.42834	1.949528
1.44492	1.949489
1.4617	1.949449
1.47867	1.94941
1.49583	1.949371
1.51319	1.949332
1.53076	1.949292
1.54853	1.949253
1.56651	1.949214
1.58469	1.949175
1.60309	1.949135
1.6217	1.949096
1.64052	1.949056
1.65957	1.949016
1.67883	1.948976
1.69832	1.948936
1.71804	1.948896
1.73798	1.948855
1.75816	1.948815
1.77857	1.948773
1.79921	1.948732
1.8201	1.94869
1.84123	1.948648
1.8626	1.948606
1.88423	1.948563
1.9061	1.948519
1.92823	1.948476
1.95061	1.948431
1.97325	1.948387
1.99616	1.948341
2.01933	1.948296
2.04278	1.948249
2.06649	1.948202
2.09048	1.948155
2.11475	1.948107
2.1393	1.948058
2.16413	1.948008
2.18925	1.947958
2.21467	1.947907
2.24038	1.947855
2.26638	1.947803
2.29269	1.947749
2.31931	1.947695
2.34623	1.94764
2.37347	1.947584
2.40102	1.947527
2.42889	1.947469
2.45709	1.94741
2.48561	1.947349
2.51447	1.947288
2.54366	1.947226
2.57319	1.947163
2.60306	1.947098
2.63328	1.947032
2.66384	1.946965
2.69477	1.946897
2.72605	1.946827
2.7577	1.946756
2.78971	1.946684
2.82209	1.94661
2.85486	1.946535
2.888	1.946458
2.92152	1.94638
2.95544	1.9463
2.98975	1.946218
3.02445	1.946135
3.05956	1.94605
3.09508	1.945963
3.13101	1.945874
3.16736	1.945784
3.20412	1.945691
3.24132	1.945597
3.27895	1.945501
3.31701	1.945402
3.35552	1.945301
3.39447	1.945199
3.43388	1.945094
3.47374	1.944986
3.51406	1.944876
3.55486	1.944764
3.59612	1.94465
3.63787	1.944533
3.6801	1.944413
3.72282	1.94429
3.76604	1.944165
3.80976	1.944037
3.85398	1.943907
3.89872	1.943773
3.94398	1.943636
3.98977	1.943496
4.03608	1.943353
4.08294	1.943207
4.13033	1.943057
4.17828	1.942904
4.22679	1.942748
4.27585	1.942587
4.32549	1.942424
4.3757	1.942256
4.4265	1.942085
4.47788	1.941909
4.52987	1.94173
4.58245	1.941547
4.63565	1.941359
4.68946	1.941167
4.7439	1.94097
4.79897	1.940769
4.85468	1.940563
4.91104	1.940353
4.96805	1.940137
5.02572	1.939917
5.08406	1.939691
5.14308	1.93946
5.20278	1.939224
5.26318	1.938982
5.32428	1.938734
5.38609	1.938481
5.44861	1.938222
5.51186	1.937956
5.57585	1.937684
5.64058	1.937406
5.70606	1.937122
5.7723	1.936831
5.8393	1.936532
5.90709	1.936227
5.97566	1.935915
6.04503	1.935595
6.11521	1.935267
6.1862	1.934932
6.25801	1.934589
6.33066	1.934238
6.40415	1.933878
6.47849	1.93351
6.5537	1.933133
6.62978	1.932747
6.70674	1.932352
6.7846	1.931947
6.86336	1.931533
6.94303	1.931108
7.02363	1.930674
7.10516	1.930229
7.18765	1.929774
7.27108	1.929307
7.35549	1.92883
7.44088	1.928341
7.52726	1.92784
7.61464	1.927327
7.70303	1.926802
7.79246	1.926264
7.88292	1.925713
7.97443	1.925148
8.067	1.924571
8.16064	1.923979
8.25538	1.923372
8.35121	1.922751
8.44816	1.922115
8.54623	1.921463
8.64544	1.920796
8.7458	1.920112
8.84733	1.919412
8.95003	1.918694
9.05393	1.917959
9.15904	1.917206
9.26536	1.916434
9.37292	1.915643
9.48173	1.914833
9.5918	1.914003
9.70314	1.913152
9.81578	1.912281
9.92973	1.911388
10.045	1.910473
10.1616	1.909535
10.2796	1.908573
10.3989	1.907588
10.5196	1.906579
10.6417	1.905544
10.7653	1.904483
10.8902	1.903395
11.0167	1.902281
11.1446	1.901138
11.2739	1.899967
11.4048	1.898766
11.5372	1.897535
11.6711	1.896272
11.8066	1.894978
11.9437	1.89365
12.0823	1.892289
12.2226	1.890893
12.3645	1.889461
12.508	1.887993
12.6532	1.886487
12.8001	1.884942
12.9487	1.883357
13.099	1.881732
13.2511	1.880064
13.4049	1.878352
13.5605	1.876597
13.7179	1.874795
13.8772	1.872946
14.0383	1.871048
14.2012	1.869101
14.3661	1.867101
14.5329	1.865049
14.7016	1.862943
14.8722	1.86078
15.0449	1.858559
15.2195	1.856279
15.3962	1.853937
15.5749	1.851532
15.7557	1.849061
15.9386	1.846524
16.1237	1.843916
16.3108	1.841238
16.5002	1.838486
16.6917	1.835657
16.8855	1.83275
17.0815	1.829762
17.2798	1.82669
17.4804	1.823532
17.6833	1.820284
17.8886	1.816945
18.0963	1.81351
18.3063	1.809976
18.5189	1.806341
18.7338	1.802601
18.9513	1.798751
19.1713	1.794789
19.3939	1.79071
19.619	1.78651
19.8467	1.782186
20.0771	1.777731
20.3102	1.773143
20.546	1.768415
20.7845	1.763542
21.0258	1.75852
21.2699	1.753342
21.5168	1.748003
21.7666	1.742496
22.0192	1.736814
22.2748	1.730952
22.5334	1.7249
22.795	1.718653
23.0596	1.712201
23.3273	1.705536
23.5981	1.69865
23.8721	1.691532
24.1492	1.684172
24.4295	1.676561
24.7131	1.668686
25	1.660535

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: —

LiI (Lithium iodide): all datasets

Li 1976: n 0.25–25 µm n 0.25–25 µm default

About LiI (Lithium iodide)

Lithium iodide (LiI) is a compound that forms white, hygroscopic deliquescent crystals. In the context of optics, lithium iodide is known for its wide transmission range in the infrared spectrum. Because of its hygroscopic nature, it must be handled carefully to prevent moisture absorption, which could degrade its optical properties. LiI is less commonly used than some other alkali halides, like potassium bromide (KBr) or sodium chloride (NaCl), for infrared spectroscopy applications. However, it can still be found in specialized optical systems and sensors where its specific properties are needed.

More about LiI (Lithium iodide) →

Provenance

Version: 1 (snapshot c5c2f18)
Source page: refractiveindex.info
Original file: database/data/main/LiI/nk/Li.yml
ID: ds_0d9d8474f4dc
API: /v1/datasets/ds_0d9d8474f4dc

Plot