ASTM E131-05

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: E131 – 05
Standard Terminology Relating to
,
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Molecular Spectroscopy
This standard is issued under the fixed designation E131; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
absorption laws (see absorptivity) are due to inability to measure
1. Referenced Documents
exactly the true transmittance or to know the exact concentration of an
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1.1 ASTM Standards:
absorbing substance.
E135 Terminology Relating to Analytical Chemistry for
absorption band—a region of the absorption spectrum in
Metals, Ores, and Related Materials
which the absorbance passes through a maximum.
E168 Practices for General Techniques of Infrared Quanti-
absorption coefficient, a—a measure of absorption of radiant
tative Analysis
energy from an incident beam as it traverses an absorbing
E204 Practices for Identification of Material by Infrared
−ab
medium according to Bouguer’s law, P/P = e .
Absorption Spectroscopy, Using the ASTM Coded Band
o
and Chemical Classification Index
DISCUSSION—In IRS, a is a measure of the rate of absorption of
E284 Terminology of Appearance
energy from the evanescent wave.
E386 Practice for Data Presentation Relating to High-
absorption parameter, a—the relative reflection loss per
ResolutionNuclearMagneticResonance(NMR)Spectros-
reflection that results from the absorption of radiant energy
copy
at a reflecting surface: a=1− R, and R=the reflected
E456 Terminology Relating to Quality and Statistics
4 fraction of incident radiant power.
1.2 Other Documents:
absorption spectrum—a plot, or other representation, of
ISO Guide 30–1981 (E) Terms and definitions used in
absorbance, or any function of absorbance, against wave-
connections with reference materials
length, or any function of wavelength.
2. Terminology absorptivity, a—theabsorbancedividedbytheproductofthe
concentration of the substance and the sample pathlength,
a = A/bc. The units of b and c shall be specified.
absorbance, A—the logarithm to the base 10 of the recip-
DISCUSSION—1—The recommended unit for b is the centimetre. The
rocal of the transmittance, (T).
recommended unit for c is kilogram per cubic metre. Equivalent units
A 5log ~1/T!52log T (1) 3 3
10 10
are g/dm , g/L, or mg/cm .
DISCUSSION—2—The equivalent IUPAC term is “specific absorption
DISCUSSION—In practice the observed transmittance must be substi-
coefficient.”
tuted for T.Absorbance expresses the excess absorption over that of a
specified reference or standard. It is implied that compensation has
absorptivity, molar, ´—the product of the absorptivity, a, and
been effected for reflectance losses, solvent absorption losses, and
the molecular weight of the substance.
refractive effects, if present, and that attenuation by scattering is small
comparedwithattenuationbyabsorption.Apparentdeviationsfromthe
DISCUSSION—The equivalent IUPAC term is “molar absorption coef-
ficient.”
1 acceptanceangle, n—for an optical fiber,themaximumangle,
This terminology is under the jurisdiction of ASTM Committee E13 on
measuredfromthelongitudinalaxisorcenterlineofthefiber
Molecular Spectroscopy and Separation Science and is the direct responsibility of
Subcommittee E13.94 on Terminology.
to an incident ray, within which the ray will be accepted for
Current edition approved Dec. 12, 2005. Published September 2005. Originally
transmission along the fiber by total internal reflection.
approved in 1957. Last previous edition approved in 2002 as E131–02. DOI:
10.1520/E0131-05.
DISCUSSION—If the incidence angle exceeds the acceptance angle,
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Forotherdefinitionsrelatingtonuclearmagneticresonance,seePracticeE386.
optical power in the incident ray will be coupled into leaky modes or
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or
rays, or lost by scattering, diffusion, or absorption in the cladding. For
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
a cladded step-index fiber in the air, the sine of the acceptance angle is
Standards volume information, refer to the standard’s Document Summary page on
givenbythesquarerootofthedifferenceofthesquaresoftherefractive
the ASTM website.
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indexes of the fiber core and the cladding, that is, by the relation as
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org. follows:
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E131 – 05
2 2 DISCUSSION—This term should strictly be used with reference to a
sin A 5 = n 2 n (2)
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