1、Designation: E 131 05Standard Terminology Relating toMolecular Spectroscopy1, 2This standard is issued under the fixed designation E 131; 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 parent
2、heses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Referenced Documents1.1 ASTM Standards:3E 135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related MaterialsE 168 Practices for General Te
3、chniques of Infrared Quanti-tative AnalysisE 204 Practices for Identification of Material by InfraredAbsorption Spectroscopy, Using the ASTM Coded Bandand Chemical Classification IndexE 284 Terminology of AppearanceE 386 Practice for Data Presentation Relating to High-Resolution Nuclear Resonance (N
4、MR) SpectroscopyE 456 Terminology Relating to Quality and Statistics1.2 Other Documents:4ISO Guide 301981 (E) Terms and definitions used inconnections with reference materials2. Terminologyabsorbance, Athe logarithm to the base 10 of the recip-rocal of the transmittance, (T).A 5 log101/T! 52log10T (
5、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 prese
6、nt, 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 t
7、he absorption spectrum inwhich the absorbance passes through a maximum.absorption coefficient, aa measure of absorption of radiantenergy from an incident beam as it traverses an absorbingmedium according to Bouguers law, P/Po= eab.DISCUSSIONIn IRS, a is a measure of the rate of absorption ofenergy f
8、rom the evanescent wave.absorption parameter, athe relative reflection loss perreflection that results from the absorption of radiant energyat a reflecting surface: a=1R, and R = the reflectedfraction of incident radiant power.absorption spectruma plot, or other representation, ofabsorbance, or any
9、function of absorbance, against wave-length, 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. T
10、herecommended 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, ethe product of the absorptivity, a, andthe molecular weight of the substance.DISCUSSIONThe equivalent IUPAC t
11、erm 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 inci
12、dence 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
13、 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 angle and n1and n2are the refractive indexesof the core and cladding, respectively. If the refractive index is a function1This terminology is
14、 under the jurisdiction of ASTM Committee E13 onMolecular Spectroscopy and Chromatography and is the direct responsibility ofSubcommittee E13.94 on Terminology.Current edition approved Sept. 1, 2005. Published September 2005. Originallyapproved in 1957. Last previous edition approved in 2002 as E 13
15、1 02.2For other definitions relating to nuclear magnetic resonance, see Practice E 386.3For 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 Summar
16、y page onthe ASTM website.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.of distance from the center of the core, as in the c
17、ase of graded indexfibers, then the acceptance angle depends on the distance from the corecenter. The acceptance angle is maximum 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 st
18、ep-indexfiber as follows:sin Ar5 =n122 n22(3)where Aris the acceptance angle at a point on the entrance face at adistance, r, 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. Unles
19、s otherwise stated, acceptanceangles and numerical apertures for fiber optics are those for the center ofthe endface of the fiber, that is, where the refractive index, and hence thenumerical aperture, is the highest.accuracythe closeness of agreement between an observedvalue and an accepted referenc
20、e value (See TerminologyE 456).DISCUSSIONThe term accuracy, when applied to a set of observedvalues, will be a combination of a random component and a commonsystematic error or bias component. Since in routine use, randomcomponents and bias components cannot be completely separated, thereported “acc
21、uracy” must be interpreted as a combination of these twocomponents.active fiber optic chemical sensor, na fiber optic chemicalsensor in which a transduction mechanism other than theintrinsic spectroscopic properties of the analyte is used tomodulate the optical signal.DISCUSSIONExamples include a pH
22、 sensor composed of a chemicalindicator substance whose color changes with pH, and an oxygensensor coupled to an optical fiber bearing a chemical indicator whosefluorescence intensity depends on oxygen concentration.aliasingthe appearance of features at wavenumbers otherthan their true value caused
23、by using a sampling frequencyless than twice the highest modulation frequency in theinterferogram; also known as “folding.”analytical curvethe graphical representation of a relationbetween some function of radiant power and the concentra-tion or mass of the substance emitting or absorbing it.analyti
24、cal wavelengthany wavelength at which an absor-bance measurement is made for the purpose of the determi-nation of a constituent 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)
25、that has afrequency higher than that of the incident monochromaticbeam.aperture of an IRE, A8that portion of the IRE surface thatcan be utilized to conduct light into the IRE at the desiredangle of incidence.apodizationmodification of the ILS function by multiplyingthe interferogram by a weighting f
26、unction the magnitude ofwhich varies with retardation.DISCUSSIONThis term should strictly be used with reference to aweighting function whose magnitude is greatest at the centerburst anddecreases with retardation.attenuated total reflection (ATR)reflection that occurswhen an absorbing coupling mecha
27、nism acts in the processof total internal reflection to make the reflectance less thanunity.DISCUSSIONIn this process, if an absorbing sample is placed incontact with the reflecting surface, the reflectance for total internalreflection will be attenuated to some value between zero and unity ( OR1) i
28、n regions of the spectrum where absorption of the radiantpower can take place.attenuation index, ka measure of the absorption of 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 en
29、ergy, andn = the refractive index of the absorbing medium.backgroundapparent absorption caused by anything otherthan the substance 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 inciden
30、t on a sample at a given wavelength.basic NMR frequency, n0the frequency, measured in hertz(Hz), of the oscillating magnetic field applied to inducetransitions between nuclear magnetic energy levels.bathochromic shift, nchange of a spectral band to longerwavelength (lower frequency) because of struc
31、tural modifi-cations or environmental influence; also known as “redshift.”beamsplittera semireflecting device used to create, andoften to recombine, spatially separate beams.DISCUSSIONBeamsplitters are often made by depositing a film of ahigh refractive index material onto a flat transmitting substr
32、ate with anidentical compensator plate being held on the other side of the film.beamsplitter efficiencythe product 4RT, where R 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
33、 to theconcentration of the absorbing substance. See also absorp-tivity.biasa systematic error that contributes to the differencebetween a population mean of the measurements or testresults and an accepted or reference value (see TerminologyE 456).DISCUSSIONBias is determined by the following equati
34、on:bias 5 e 51n(i 5 1nei(4)where:n = the number of observations for which the accuracy isdetermined,ei= the difference 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 proportiona
35、l to the thickness of the sample in theoptical path.E131052DISCUSSIONBouguers law is sometimes also known as Lambertslaw.boxcar truncationidentical effective weighting of all pointsin the measured interferogram prior to the Fourier transform;all points outside of the range of the measured interferog
36、ramtake a value of zero.bufferin fiber optics, see fiber optic buffer.bulk reflectionreflection in which radiant energy is returnedexclusively from within the specimen.DISCUSSIONBulk reflection may be diffuse or specular.centerburstthe region of greatest amplitude in an interfero-gram.DISCUSSIONFor
37、unchirped or only slightly chirped interferograms,this region includes the “zero path difference point” and the “zeroretardation point.”certified reference material, na reference material, thecomposition or properties of which are certified by arecognized standardizing agency or group.DISCUSSIONA ce
38、rtified reference material produced by the NationalInstitute of Standards and Technology (NIST) is designated a StandardReference 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 resonan
39、ce at the magnetic field used in theexperiment and Dn is the frequency difference between thereference substance and the substance 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.D
40、ISCUSSIONIf the experiment is done at constant frequency (fieldsweep) the defining equation becomesd5DnnR3S1 2DnnRD3 106(6)chirpingthe process of dispersing the zero phase differencepoints for different wavelengths across the interferogram, sothat the magnitude of the signal is reduced in the short
41、regionof the interferogram where all wavelengths would otherwiseconstructively interfere.cladsee cladding.cladding, nof an optical 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 intern
42、al reflection.DISCUSSIONThe cladding confines electromagnetic waves to thecore, provides some protection to the core, and also 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 sol
43、ution work, the recommended unit of concen-tration is grams of solute per litre of solution.core, nof an optical fiber, the center region of an opticalwaveguide through which radiant energy is transmitted.DISCUSSIONIn a dielectric waveguide such as an optical fiber, therefractive index of the core m
44、ust be higher than that of the cladding.Most of the radiant energy is confined to the core.correlation coefficient (r)a measure 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
45、X and Y.DISCUSSIONXiand Yiare any two mean corrected variables. For thesimple linear regression only,rxy5 R 5 sign of b1!R2!1/2(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 t
46、hegreater to the lesser refractive medium: uc= sin1n21, wheren21= the ratio of the refractive indices of the two media.DISCUSSIONTotal 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.de
47、pth of penetration, dpin internal reflection spectroscopy,the distance into the less refractive medium at which theamplitude of 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/
48、n1= wavelength of radiant energy in thesample; and u = angle of incidence.derivative absorption spectruma plot of rate of change ofabsorbance or of any function of absorbance with respect towavelength or any function of wavelength, against wave-length or any function of wavelength.difference absorpt
49、ion 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 E 284).digitizationthe conversion of an analog signal to digitalvalues using an analog-to-digital converter “sampling” or“digital sampling.”digitization noisethe noise generated in an interferogramthrough the use of
