ASTM E131-02

Standard Terminology Relating to Molecular Spectroscopy

General Information

• Status: Historical
• Publication Date: 09-Sep-2002
• ICS: 01.040.71 - Chemical technology (Vocabularies)
• ICS: 71.040.50 - Physicochemical methods of analysis
• Technical Committee: E13 - Molecular Spectroscopy and Separation Science

Relations

• Replaces: ASTM E131-00a - Standard Terminology Relating to Molecular Spectroscopy
• Effective Date: 10-Sep-2002
• Replaced By: ASTM E131-05 - Standard Terminology Relating to Molecular Spectroscopy
• Effective Date: 01-Sep-2005
• Referred By: ASTM E1865-97(2021) - Standard Guide for Open-Path Fourier Transform Infrared (OP/FT-IR) Monitoring of Gases and Vapors in Air
• Effective Date: 10-Sep-2002
• Referred By: ASTM E1683-02(2022) - Standard Practice for Testing the Performance of Scanning Raman Spectrometers
• Effective Date: 10-Sep-2002
• Referred By: ASTM D7414-22 - Standard Test Method for Condition Monitoring of Oxidation in In-Service Petroleum and Hydrocarbon Based Lubricants by Trend Analysis Using Fourier Transform Infrared (FT-IR) Spectrometry
• Effective Date: 10-Sep-2002
• Referred By: ASTM E925-09(2022) - Standard Practice for Monitoring the Calibration of Ultraviolet-Visible Spectrophotometers whose Spectral Bandwidth does not Exceed 2 nm
• Effective Date: 10-Sep-2002
• Referred By: ASTM D5831-17 - Standard Practice for Screening Fuels in Soils
• Effective Date: 10-Sep-2002
• Referred By: ASTM E168-16(2023) - Standard Practices for General Techniques of Infrared Quantitative Analysis
• Effective Date: 10-Sep-2002
• Referred By: ASTM D6645-18 - Standard Test Method for Methyl (Comonomer) Content in Polyethylene by Infrared Spectrophotometry
• Effective Date: 10-Sep-2002
• Referred By: ASTM D6748-22 - Standard Test Method for Determination of Potential Instability of Middle Distillate Fuels Caused by the Presence of Phenalenes and Phenalenones (Rapid Method by Portable Spectrophotometer)
• Effective Date: 10-Sep-2002
• Referred By: ASTM D8470-22 - Standard Practice for Development and Implementation of Instrument Performance Tests for Use on Multivariate Online, At-Line and Laboratory Spectroscopic Based Analyzer Systems
• Effective Date: 10-Sep-2002
• Referred By: ASTM E1653-94(2021) - Standard Guide for Specifying Dynamic Characteristics of Optical Radiation Transmitting Fiber Waveguides
• Effective Date: 10-Sep-2002
• Referred By: ASTM E3029-15(2023) - Standard Practice for Determining Relative Spectral Correction Factors for Emission Signal of Fluorescence Spectrometers
• Effective Date: 10-Sep-2002
• Referred By: ASTM E2224-23a - Standard Guide for Forensic Analysis of Fibers by Infrared Spectroscopy
• Effective Date: 10-Sep-2002
• Referred By: ASTM D7210-21 - Standard Practice for Extraction of Additives in Polyolefin Plastics
• Effective Date: 10-Sep-2002

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E 131 – 02
Standard Terminology Relating to
,
1 2
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 (e) indicates an editorial change since the last revision or reapproval.
the molecular weight of the substance.
absorbance, A— the logarithm to the base 10 of the
DISCUSSION—The equivalent IUPAC term is “molar absorption coef-
reciprocal of the transmittance, (T).
ficient.”
A 5log ~1/T!52log T (1)
10 10
acceptanceangle, n—for an optical fiber,themaximumangle,
DISCUSSION—In practice the observed transmittance must be substi-
measuredfromthelongitudinalaxisorcenterlineofthefiber
tuted for T. Absorbance expresses the excess absorption over that of a
to an incident ray, within which the ray will be accepted for
specified reference or standard. It is implied that compensation has
transmission along the fiber by total internal reflection.
been effected for reflectance losses, solvent absorption losses, and
refractive effects, if present, and that attenuation by scattering is small DISCUSSION—If the incidence angle exceeds the acceptance angle,
comparedwithattenuationbyabsorption.Apparentdeviationsfromthe optical power in the incident ray will be coupled into leaky modes or
absorption laws (see absorptivity) are due to inability to measure rays, or lost by scattering, diffusion, or absorption in the cladding. For
exactly the true transmittance or to know the exact concentration of an a cladded step-index fiber in the air, the sine of the acceptance angle is
absorbing substance. givenbythesquarerootofthedifferenceofthesquaresoftherefractive
indexes of the fiber core and the cladding, that is, by the relation as
absorption band—a region of the absorption spectrum in
follows:
which the absorbance passes through a maximum.
2 2
sin A 5 n 2 n (2)
=
1 2
absorption coefficient, a—a measure of absorption of radiant
energy from an incident beam as it traverses an absorbing
where A is the acceptance angle and n and n are the refractive indexes
−ab
1 2
medium according to Bouguer’s law, P/P = e .
o
of the core and cladding, respectively. If the refractive index is a function
of distance from the center of the core, as in the case of graded index
DISCUSSION—In IRS, a is a measure of the rate of absorption of
fibers, then the acceptance angle depends on the distance from the core
energy from the evanescent wave.
center. The acceptance angle is maximum at the center, and zero at the
absorption parameter, a—the relative reflection loss per
core-cladding boundary.At any radius, r, the sine of the acceptance angle
reflection that results from the absorption of radiant energy of a graded index fiber is defined in compliance with that of a step-index
fiber as follows:
at a reflecting surface: a=1− R, and R=the reflected
fraction of incident radiant power.
2 2
sin A 5=n 2 n (3)
r 1 2
absorption spectrum—a plot, or other representation, of
absorbance, or any function of absorbance, against wave-
where A is the acceptance angle at a point on the entrance face at a
r
length, or any function of wavelength. distance, r, from the center, n is the refractive index of the core at a
r
radius, r, and n is the refractive index of the cladding. In air, sin A and
absorptivity, a— the absorbance divided by the product of the
2
sin A are the numerical apertures. Unless otherwise stated, acceptance
r
concentration of the substance and the sample pathlength,
angles and numerical apertures for fiber optics are those for the center of
a = A/bc. The units of b and c shall be specified.
the endface of the fiber, that is, where the refractive index, and hence the
numerical aperture, is the highest.
DISCUSSION—1—The recommended unit for b is the centimetre. The
recommended unit for c is kilogram per cubic metre. Equivalent units
accuracy—the closeness of agreement between an observed
3 3
are g/dm , g/L, or mg/cm .
value and an accepted reference value (See Terminology
DISCUSSION—2—The equivalent IUPAC term is “specific absorption
3
E456) .
coefficient.”
DISCUSSION—The term accuracy, when applied to a set of observed
absorptivity, molar, e—the product of the absorptivity, a, and
values, will be a combination of a random component and a common
systematic error or bias component. Since in routine use, random
components and bias components cannot be completely separated, the
1
This terminology is under the jurisdiction of ASTM Committee E-13 on
reported “accuracy” must be interpreted as a combination of these two
Molecular Spectroscopy and is the direct responsibility of Subcommittee E13.04 on
components.
Nomenclature.
Current edition approved Sept. 10, 2002.
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