tan_1998 ======== C\. Z\. Tan, "Determination of refractive index of silica glass for infrared wavelengths by IR spectroscopy", J\. Non\-Cryst\. Solids 223, 158 \(1998\) `Source record `__ · :doc:`Catalogue ` · :doc:`Review register ` DOI: `10\.1016/s0022\-3093\(97\)00438\-9 `__ **Source kind:** measurement **Recorded technique:** Channelled\-spectrum \(Fabry\-Perot fringe\) interferometry in an FT\-IR transmission spectrum\: a silica\-glass disk \(Suprasil 2, ~1000 ppm OH\), 15 mm diameter, 230 um thick \(gauge, \+\-1 um; thickness variation within 2 um\), both faces polished, Perkin Elmer System 2000 FT\-IR, 1000 scans, 4 cm\-1 resolution\. n at each transmission maximum from n\(lambda\_\(m\-i\)\) = \(m \- i\) lambda\_\(m\-i\)/\(2h\) \(Eq\. 6\), the order fixed by the fringe at lambda\_m = 3\.1174 um, where Malitson's Eq\. \(1\) gives the order m = 209 \(pp\. 160\-162\)\. **Materials in structured entries:** None recorded. **Dataset quantities:** None recorded. **Contents:** 0 datasets; 0 formulas. Curation notes -------------- Pages 158\-163 are pdf pages 1\-6\. Identity checked against the first page\. Nothing is tabulated\: the measured indices, 3\-6\.7 um, are shown only in Fig\. 5 \(open circles, with Malitson's Eq\. \(1\) as the curve; figure not digitised\), so the record has no datasets\. Fig\. 3 is the 230\-um plate's transmission spectrum \(OH band at 3672 cm\-1, CO2 on the surface at 2350 and 2393 cm\-1, OH and water bands at 2259\-1632 cm\-1\); Fig\. 4 typical fringes; Figs\. 1\-2 schematics\. WHAT THE TEXT STATES\. Fringes are seen from 3 to 6\.7 um except in the CO2 bands and at 4\.7\-5 um, where the missing fringes are counted from the fringe spacing; they vanish at 7\.08\-7\.4 um \(where n from Kramers\-Kronig analysis approaches 1\) and reappear beyond 7\.4 um, where the method is not applied \(p\. 162\)\. 'In the overlapping region \[3\-3\.7 um\], the error of the evaluated refractive indices is found to be within \+\-0\.0005'; 'the accuracy for determination of refractive index can approach ~10^\-3' \(\+\-1 um in the thickness\), the experimental error '\(~\+\-10^\-3\)' \(pp\. 162\-163\)\. 'For silica glass, the evaluated refractive indices in the investigated wavelength region are exactly equal to the extrapolation results of Eq\. \(1\)' \(p\. 162\)\: the evidence refractiveindex\.info cites for using Malitson's formula to 6\.7 um\. The OH content \(~1000 ppm\) and sample preparation are argued to be negligible at this accuracy \(Eqs\. 9\-10, p\. 163\)\. FORMULA\. Eq\. \(1\) is Malitson's three\-term Sellmeier equation reproduced \(coefficients identical to malitson\_1965/sellmeier, with the range printed 0\.213856\-3\.7067 um\); it is not recorded again\. The reference to Malitson is printed 'J\. Opt\. Soc\. Am\. 53 \(1965\) 1205' \(volume 55\)\. **Recorded bibliographic identity status:** VALIDATED\_WITH\_WARNINGS. This concerns identification of the source; it does not establish the scientific correctness of its contents. Datasets -------- No datasets are recorded. Formulas -------- No formulas are recorded. Corrections ----------- No dataset errata are recorded in this source record. Formula corrections, where recorded, appear with their formulas above. Curation notes may also discuss corrections or unresolved interpretation. Consult the :doc:`review register ` for the checks and decisions.