1、Designation: E131 10Standard 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 parenthe
2、ses 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 S
3、tandards:3E135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related MaterialsE168 Practices for General Techniques of Infrared Quanti-tative AnalysisE204 Practices for Identification of Material by InfraredAbsorption Spectroscopy, Using the ASTM Coded Bandand Chemical Classifica
4、tion IndexE284 Terminology of AppearanceE386 Practice for Data Presentation Relating to High-Resolution Nuclear Magnetic Resonance (NMR) Spectros-copyE456 Terminology Relating to Quality and Statistics2.2 Other Documents:4ISO Guide 301981 (E) Terms and definitions used in con-nections with reference
5、 materials3. Terminologyabsorbance, Athe logarithm to the base 10 of the recip-rocal of the transmittance, (T).A 5 log101/T! 52log10T (1)DISCUSSIONIn practice the observed transmittance must be substi-tuted for T. Absorbance expresses the excess absorption over that of aspecified reference or standa
6、rd. 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 inab
7、ility 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, aa measure of absorption of radiantenergy from an incident beam as it
8、traverses an absorbingmedium according to Bouguers law, P/Po= eab.DISCUSSIONIn IRS, a 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:
9、a=1R, and R = the reflectedfraction of incident radiant power.absorption spectruma plot, or other representation, ofabsorbance, or any function of absorbance, against wave-length, or any function of wavelength.absorptivity, a the absorbance divided by the product of theconcentration of the substance
10、 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 absorptioncoefficie
11、nt.”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
12、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
13、 the cladding. Fora cladded step-index fiber in the air, the sine of the acceptance angle is1This 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
14、 March 1, 2010. Published April 2010. Originallyapproved in 1957. Last previous edition approved in 2005 as E131 05. DOI:10.1520/E0131-10.2For other definitions relating to nuclear magnetic resonance, see Practice E386.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact A
15、STM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM
16、 International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.given 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:sin A 5 = n122 n22(2)where A is the acceptance
17、 angle and n1and n2are the refractive indexesof the core and cladding, respectively. If the refractive index is a functionof distance from the center of the core, as in the case of graded indexfibers, then the acceptance angle depends on the distance from the corecenter. The acceptance angle is maxi
18、mum at the center, and zero at thecore-cladding boundary. At any radius, r, the sine of the acceptance angleof a graded index fiber is defined in compliance with that of a step-indexfiber as follows:sin Ar5 =n122 n22(3)where Aris the acceptance angle at a point on the entrance face at adistance, r,
19、from the center, nris the refractive index of the core at aradius, r, and n2is the refractive index of the cladding. In air, sin A andsin Arare the numerical apertures. Unless otherwise stated, acceptanceangles and numerical apertures for fiber optics are those for the center ofthe endface of the fi
20、ber, that is, where the refractive index, and hence thenumerical aperture, is the highest.accuracythe closeness of agreement between an observedvalue and an accepted reference value (see TerminologyE456).DISCUSSIONThe term accuracy, when applied to a set of observedvalues, will be a combination of a
21、 random component and a commonsystematic error or bias component. Since in routine use, randomcomponents and bias components cannot be completely separated, thereported “accuracy” must be interpreted as a combination of these twocomponents.active fiber optic chemical sensor, na fiber optic chemicals
22、ensor in which a transduction mechanism other than theintrinsic spectroscopic properties of the analyte is used tomodulate the optical signal.DISCUSSIONExamples include a pH sensor composed of a chemicalindicator substance whose color changes with pH, and an oxygensensor coupled to an optical fiber
23、bearing a chemical indicator whosefluorescence intensity depends on oxygen concentration.aliasingthe appearance of features at wavenumbers otherthan their true value caused by using a sampling frequencyless than twice the highest modulation frequency in theinterferogram; also known as “folding.”anal
24、ytical curvethe graphical representation of a relationbetween some function of radiant power and the concentra-tion or mass of the substance emitting or absorbing it.analytical wavelengthany wavelength at which an absor-bance measurement is made for the purpose of the determi-nation of a constituent
25、 of a sample.angle of incidence, uthe angle between an incident radiantbeam and a perpendicular to the interface between twomedia.anti-Stokes line (band)a Raman line (band) that has afrequency higher than that of the incident monochromaticbeam.aperture of an IRE, A8that portion of the IRE surface th
26、atcan be utilized to conduct light into the IRE at the desiredangle of incidence.apodizationmodification of the ILS function by multiplyingthe interferogram by a weighting function the magnitude ofwhich varies with retardation.DISCUSSIONThis term should strictly be used with reference to aweighting
27、function whose magnitude is greatest at the centerburst anddecreases with retardation.attenuated total reflection (ATR)reflection that occurswhen an absorbing coupling mechanism acts in the processof total internal reflection to make the reflectance less thanunity.DISCUSSIONIn this process, if an ab
28、sorbing sample is placed incontact with the reflecting surface, the reflectance for total internalreflection will be attenuated to some value between zero and unity ( OR1) in regions of the spectrum where absorption of the radiantpower can take place.attenuation index, ka measure of the absorption o
29、f radiantenergy by an absorbing material. k is related to the absorp-tion coefficient by: nk = aco/4pn, where co= the speed oflight in vacuo, n = the frequency of radiant energy, andn = the refractive index of the absorbing medium.backgroundapparent absorption caused by anything otherthan the substa
30、nce for which the analysis is being made.baselineany line drawn on an absorption spectrum to estab-lish a reference point representing a function of the radiantpower incident on a sample at a given wavelength.basic NMR frequency, n0the frequency, measured in hertz(Hz), of the oscillating magnetic fi
31、eld applied to inducetransitions between nuclear magnetic energy levels.bathochromic shift, nchange of a spectral band to longerwavelength (lower frequency) because of structural modifi-cations or environmental influence; also known as “redshift.”beamsplittera semireflecting device used to create, a
32、ndoften to recombine, spatially separate beams.DISCUSSIONBeamsplitters are often made by depositing a film of ahigh refractive index material onto a flat transmitting substrate with anidentical compensator plate being held on the other side of the film.beamsplitter efficiencythe product 4RT, where R
33、 is thereflectance and T is the transmittance of the beamsplitter.Beers lawthe absorbance of a homogeneous sample con-taining an absorbing substance is directly proportional to theconcentration of the absorbing substance (see also absorp-tivity )biasa systematic error that contributes to the differe
34、ncebetween a population mean of the measurements or testresults and an accepted or reference value (see TerminologyE456).DISCUSSIONBias is determined by the following equation:bias 5 e 51n(i 5 1nei(4)where:n = the number of observations for which the accuracy isdetermined,E131 102ei= the difference
35、between a measured value of a propertyand its accepted reference value, ande = the mean value of all the ei.Bouguers lawthe absorbance of a homogeneous sample isdirectly proportional to the thickness of the sample in theoptical path.DISCUSSIONBouguers law is sometimes also known as Lambertslaw.boxca
36、r truncationidentical effective weighting of all pointsin the measured interferogram prior to the Fourier transform;all points outside of the range of the measured interferogramtake a value of zero.bufferin fiber optics, see fiber optic buffer.bulk reflectionreflection in which radiant energy is ret
37、urnedexclusively from within the specimen.DISCUSSIONBulk reflection may be diffuse or specular.centerburstthe region of greatest amplitude in an interfero-gram.DISCUSSIONFor unchirped or only slightly chirped interferograms,this region includes the “zero path difference point” and the “zeroretardati
38、on point.”certified reference material, na reference material, thecomposition or properties of which are certified by arecognized standardizing agency or group.DISCUSSIONA certified reference material produced by the NationalInstitute of Standards and Technology (NIST) is designated a StandardRefere
39、nce Material (SRM).chemical shift (NMR), dthe defining equation for d is thefollowing:d5DnnR3 106(5)where nRis the frequency with which the reference sub-stance is in resonance at the magnetic field used in theexperiment and Dn is the frequency difference between thereference substance and the subst
40、ance whose chemical shift isbeing determined, at constant field. The sign of Dn is to bechosen such that shifts to the high frequency side of thereference shall be positive.DISCUSSIONIf the experiment is done at constant frequency (fieldsweep) the defining equation becomesd5DnnR3S1 2DnnRD3 106(6)chi
41、rpingthe process of dispersing the zero phase differencepoints for different wavelengths across the interferogram, sothat the magnitude of the signal is reduced in the short regionof the interferogram where all wavelengths would otherwiseconstructively interfere.cladsee cladding.cladding, nof an opt
42、ical fiber, a layer of a opticallytransparent lower refractive index material in intimate con-tact with a core of higher refractive index material used toachieve total internal reflection.DISCUSSIONThe cladding confines electromagnetic waves to thecore, provides some protection to the core, and also
43、 transmits evanes-cent waves that usually are bound to waves in the core.concentration, cthe quantity of the substance contained in aunit quantity of sample.DISCUSSIONFor solution work, the recommended unit of concen-tration is grams of solute per litre of solution.core, nof an optical fiber, the ce
44、nter region of an opticalwaveguide through which radiant energy is transmitted.DISCUSSIONIn a dielectric waveguide such as an optical fiber, therefractive index of the core must be higher than that of the cladding.Most of the radiant energy is confined to the core.correlation coefficient (r)a measur
45、e of the strength of thelinear relationship between X and Y, calculated by theequation:rxy5(i 5 1nXiYi!(i 5 1nXi2!1/2(i 5 1nYi2!1/2(7)where:n = the number of observations in X and Y.DISCUSSIONXiand Yiare any two mean corrected variables. For thesimple linear regression only,rxy5 R 5 sign of b1!R2!1/
46、2(8)where:R2= the coefficient of multiple determination.critical angle, ucthe angle whose sine is equal to the relativerefractive index for light striking an interface from thegreater to the lesser refractive medium: uc= sin1n21, wheren21= the ratio of the refractive indices of the two media.DISCUSS
47、IONTotal reflection occurs when light is reflected in themore refractive of two media from the interface between them at anyangle of incidence exceeding the critical angle.depth of penetration, dpin internal reflection spectroscopy,the distance into the less refractive medium at which theamplitude o
48、f the evanescent wave is e1(that is, 36.8 %) ofits value at the surface:dp5l12psin2u2h212!1/2(9)where: n21=n2/n1= refractive index of sample divided bythat of the IRE; l1= l/n1= wavelength of radiant energy in thesample; and u = angle of incidence.derivative absorption spectruma plot of rate of chan
49、ge ofabsorbance or of any function of absorbance with respect towavelength or any function of wavelength, against wave-length or any function of wavelength.difference absorption spectruma plot of the differencebetween two absorbances or between any function of twoabsorbances, against wavelength or any function of wave-length.diffuse reflectionreflection in which the flux is scattered inmany directions by diffusion at or below the surface (seeTerminology E284).digitizationthe conversion of an a
