ASTM_E_131_-_10_2015.pdf

Designation:E13110(Reapproved 2015)Standard Terminology Relating toMolecular Spectroscopy1,2This standard is issued under the fixed designation E131;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.2.Referenced Documents2.1 ASTM Standards:3E135 Terminology Relating to Analytical Chemistry forMetals,Ores,and Related MaterialsE168 Practices for General Techniques of Infrared Quanti-tative Analysis(Withdrawn 2015)4E204 Practices for Identification of Material by InfraredAbsorption Spectroscopy,Using the ASTM Coded Bandand Chemical Classification Index(Withdrawn 2014)4E284 Terminology of AppearanceE386 Practice for Data Presentation Relating to High-Resolution Nuclear Magnetic Resonance(NMR)Spec-troscopyE456 Terminology Relating to Quality and Statistics2.2 Other Documents:5ISO Guide 301981(E)Terms and definitions used in con-nections with reference materials3.Terminologyabsorbance,Athe logarithm to the base 10 of the reciprocalof the transmittance,(T).A 5 log101/T!5 2log10T(1)DISCUSSIONIn practice the observed transmittance must be substi-tuted for T.Absorbance expresses the excess absorption over that of aspecified reference or standard.It is implied that compensation hasbeen effected for reflectance losses,solvent absorption losses,andrefractive effects,if present,and that attenuation by scattering is smallcompared with attenuation by absorption.Apparent deviations from theabsorption laws(see absorptivity)are due to inability to measureexactly the true transmittance or to know the exact concentration of anabsorbing substance.absorption banda region of the absorption spectrum inwhich the absorbance passes through a maximum.absorption coefficient,a measure of absorption of radiantenergy from an incident beam as it traverses an absorbingmedium according to Bouguers law,P/Po=eb.DISCUSSIONIn IRS,is a measure of the rate of absorption ofenergy from the evanescent wave.absorption parameter,athe relative reflection loss perreflection that results from the absorption of radiant energyat a reflecting surface:a=1 R,and R=the reflectedfraction of incident radiant power.absorption spectruma plot,or other representation,ofabsorbance,or any function of absorbance,againstwavelength,or any function of wavelength.absorptivity,a the absorbance divided by the product of theconcentration of the substance and the sample pathlength,a=A bc.The units of b and c shall be specified.DISCUSSION1The recommended unit for b is the centimetre.Therecommended unit for c is kilogram per cubic metre.Equivalent unitsare g/dm3,g/L,or mg/cm3.DISCUSSION2The equivalent IUPAC term is“specific absorptioncoefficient.”absorptivity,molar,the product of the absorptivity,a,andthe molecular weight of the substance.DISCUSSIONThe equivalent IUPAC term is“molar absorption coef-ficient.”acceptance angle,nfor an optical fiber,the maximum angle,measured from the longitudinal axis or centerline of the fiberto an incident ray,within which the ray will be accepted fortransmission along the fiber by total internal reflection.DISCUSSIONIf the incidence angle exceeds the acceptance angle,optical power in the incident ray will be coupled into leaky modes orrays,or lost by scattering,diffusion,or absorption in the cladding.Fora cladded step-index fiber in the air,the sine of the acceptance angle isgiven by the square root of the difference of the squares of the refractiveindexes of the fiber core and the cladding,that is,by the relation asfollows:1This terminology is under the jurisdiction of ASTM Committee E13 onMolecular Spectroscopy and Separation Science and is the direct responsibility ofSubcommittee E13.94 on Terminology.Current edition approved May 1,2015.Published June 2015.Originallyapproved in 1957.Last previous edition approved in 2010 as E131 10.DOI:10.1520/E0131-10R15.2For other definitions relating to nuclear magnetic resonance,see Practice E386.3For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.4The last approved version of this historical standard is referenced onwww.astm.org.5Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 sin A 5=n122 n22(2)where A is the acceptance angle and n1and n2are the refractive in-dexes of the core and cladding,respectively.If the refractive index is afunction of distance from the center of the core,as i