Definitive data on the absorption spectrum of pure water from 380 to 700 nm have been obtained with an integrating cavity technique. The results are in good agreement with those recently obtained by our group with a completely independent photothermal technique. As before, we find that the absorption in the blue is significantly lower than had previously been generally believed and that the absorption minimum is at a significantly shorter wavelength, i.e., 0.0044 ? 0.0006 m(-1) at 418 nm. Several spectroscopic features have been identified in the visible spectrum to our knowledge for the first time.

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Absorption spectrum (380–700 nm) of pure water. II. Integrating cavity measurements

A new UV submersible spectroradiometer has been employed to determine the diffuse attenuation coefficient for irradiance in the clearest natural waters [K;(X)] with emphasis on the spectral region from 300 to 400 nm. K (X) can be related to the inherent optical properties of pure water, in particular the total absorption coefficient a,,(X) and the molecular scattering coefficient bm(X), by means of equations derived from radiative transfer theory. We present an analysis showing that limiting values of K. (X) can be estimated from aw(X) and vice versa. Published a (X) data, which show discrepancies much larger than their estimated accuracies, are briefly reviewed and then compared, via our analysis, with K, (X) data (our own new and previously published data as well as relevant data of others). This comparative analysis and new data allow a consistent and accurate set of optical properties for the clearest natural waters and for pure fresh water and saltwater to be estimated from 300 to 800 nm.

Optical properties of the clearest natural waters (200–800 nm)

CRYSTALLINE MATERIALS Introduction Physical Properties Optical Properties Mechanical Properties Thermal Properties Magnetooptic Properties Electrooptic Properties Elastooptic Properties Nonlinear Optical Properties GLASSES Introduction Commercial Optical Glasses Specialty Optical Glasses Fused Silica Fluoride Glasses Chalcogenide Glasses Magnetooptic Properties Electrooptic Properties Elastooptic Properties Nonlinear Optical Properties Special Glasses POLYMERIC MATERIALS Optical Plastics Index of Refraction Nonlinear Optical Properties Thermal Properties Engineering Data METALS Physical Properties of Selected Metals Optical Properties Mechanical Properties Thermal Properties Mirror Substrate Materials LIQUIDS Introduction Water Physical Properties of Selected Liquids Index of Refraction Nonlinear Optical Properties Magnetooptic Properties Commercial Optical Liquids GASES Introduction Physical Properties of Selected Gases Index of Refraction Nonlinear Optical Properties Magnetooptic Properties Atomic Resonance Filters APPENDICES Safe Handling of Optical Materials Abbreviations, Acronyms, and Mineralogical or Common Names for Optical Materials Abbreviations for Methods of Preparing Optical Materials and Thin Films Fundamental Physical Constants Units and Conversion Factors

/pdf/handbook-of-optical-materials-3e2ukwmx2l.pdf

Handbook of Optical Materials

This paper reviews the theory and applications of photoacoustic (also called optoacoustic) methods belonging to the more general area of photothermal measurement techniques. The theory covers excitation of gaseous or condensed samples with modulated continuous light beams or pulsed light beams. The applications of photoacoustic methods include spectroscopy, monitoring deexcitation processes, probing physical properties of materials, and generating mechanical motions. Several other related photothermal methods, as well as particle-acoustics and wave-acoustics methods are also described. This review complements an earlier and narrower review [Rev. Mod. Phys. 53, 517 (1981)] that is mainly concerned with sensitive detection by pulsed photoacoustic spectroscopy in condensed matter.

Applications of photoacoustic sensing techniques

The apparent optical properties (AOPs) of oceanic case 1 waters were previously analyzed [Morel, 1988] and statistically related to the chlorophyll concentration ([Chl]) used as a global index describing the trophic conditions of water bodies. From these empirical relationships a bio-optical model of the upper layer was developed. With objectives and structure similar to those of the previous study the present reappraisal utilizes AOPs determined during recent Joint Global Ocean Flux Study cruises, namely, spectral attenuation for downward irradiance Kd(X) and irradiance reflectance R(X). This revision also benefits from improved knowledge of inherent optical properties (lOPs), namely, pure water absorption coefficients and particle scattering and absorption coefficients, and from better pigment quantification (via a systematic use of highperformance liquid chromatography). Nonlinear trends, already observed between optical properties and algal biomass, are fully confirmed, yet with numerical differences. The previous Kd(X) model, and subsequently the R(X) model, is modified to account for these new relationships. The R(X) values predicted as a function of [Chl] and the predicted ratios of reflectances at two wavelengths, which are commonly used in ocean color algorithms, compare well with field values (not used when developing the reflectance model). This good agreement means that semianalytical ocean color algorithms can be successfully applied to satellite data. Going further into purely analytical approaches, ideally based on radiative transfer computations combined with a suite of relationships between the lOPs and [Chl], remains presently problematic, especially because of the insufficient knowledge of the phase function and backscattering efficiency of oceanic particles.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2000JC000319

Bio-optical properties of oceanic waters: A reappraisal

A pulsed dye-laser optoacoustic spectroscopy technique has been used to measure the absorption spectra of light and heavy water at 21.5 degrees C in the visible region. Basic principles of pulsed optoacoustic spectroscopy technique and the procedure for absolute calibration are discussed with reference to its application in water. Experimental details of the application of optoacoustic spectroscopy to water are given. Our absorption coefficients, of accuracies about +/- 10%, are believed to be the most reliable so far. Light water has a broad absorption minimum near 475 nm where the absorption coefficient is 1.8 x 10(-4) cm(-1). Heavy water exhibits a totally different absorption spectrum and has a broad absorption minimum near 600 nm where the absorption coefficient is 1.9 x 10(-4) cm(-1). Previous measurements of the optical spectra of water were done mostly by long-path transmission measurements, and they display disagreement by factors as large as 10 near the green absorption minimum of light water. We give a critical comparison of our optoacoustic absorption spectra with other existing data.

C. K. N. Patel

Papers

Optical absorptions of light and heavy water by laser optoacoustic spectroscopy