ASTM E2529-06e1
Standard Guide for Testing the Resolution of a Raman Spectrometer

Standard No.

ASTM E2529-06e1

Release Date

2006

Published By

American Society for Testing and Materials (ASTM)

Status

Be replaced

Replace By

ASTM E2529-06(2014)

Latest

ASTM E2529-06(2022)

Scope

4.1 Assessment of the spectrometer resolution and instrument line shape (ILS) function of a Raman spectrometer is important for intercomparability of spectra obtained among widely varying spectrometer systems, if spectra are to be transferred among systems, if various sampling accessories are to be used, or if the spectrometer can be operated at more than one laser excitation wavelength.

4.2 Low-pressure discharge lamps (pen lamps such as mercury, argon, or neon) provide a low-cost means to provide both resolution and wave number calibration for a variety of Raman systems over an extended wavelength range.

4.3 There are several disadvantages in the use of emission lines for this purpose, however.

4.3.1 First, it may be difficult to align the lamps properly with the sample position leading to distortion of the line, especially if the entrance slit of the spectrometer is underfilled or not symmetrically illuminated.

4.3.2 Second, many of the emission sources have highly dense spectra that may complicate both resolution and wave number calibration, especially on low-resolution systems.

4.3.3 Third, a significant contributor to line broadening of Raman spectral features may be the excitation laser line width itself, a component that is not assessed when evaluating the spectrometer resolution with pen lamps.

4.3.4 An alternative would use a Raman active compound in place of the emission source. This compound should be chemically inert, stable, and safe and ideally should provide Raman bands that are evenly distributed from 0 cm^-1 (Raman shift) to the C-H stretching region 3000 cm ^-1 and above. These Raman bands should be of varying bandwidth.

4.4 To date, no such ideal sample has been identified; however carbon tetrachloride (see Practice E1683) and naphthalene (see Guide E1840) have been used previously for both resolution and Raman shift calibration.

4.5 The use of calcite to assess the resolution of a Raman system will be addressed in this guide. Calcite is a naturally occurring mineral that possesses many of the desired optical properties for a Raman resolution standard and is inexpensive, safe, and readily available.

4.6 The spectral bandwidth of dispersive Raman spectrometers is determined primarily by the focal length of the spectrometer, the dispersion of the grating, and the slit width. Field portable systems typically operate with fixed slits and gratings and thus operate with a fixed spectral bandwidth, while in many laboratory systems the slit widths and gratings are variable. The spectral bandwidth of Fourier-Transform (FT)-Raman systems is continuously variable by altering the optical path difference of the interferometer and furthermore is capable of obtaining much lower spectral bandwidth than most practical dispersive systems. Therefore, data obtained of a narrow Raman band on a FT-Raman system can be used to determine the resolution of a dispersive Raman ......

ASTM E2529-06e1 Referenced Document

• ANSI Z136.1 American National Standard for Safe Use of Lasers
• ASTM E131 Standard Definitions of Terms and Symbols Relating to Molecular Spectroscopy
• ASTM E1683 Standard Practice for Testing the Performance of Scanning Raman Spectrometers
• ASTM E1840 Standard Guide for Raman Shift Standards for Spectrometer Calibration

ASTM E2529-06e1 history

• 2022 ASTM E2529-06(2022) Standard Guide for Testing the Resolution of a Raman Spectrometer
• 2014 ASTM E2529-06(2014) Standard Guide for Testing the Resolution of a Raman Spectrometer
• 2006 ASTM E2529-06e1 Standard Guide for Testing the Resolution of a Raman Spectrometer
• 2006 ASTM E2529-06 Standard Guide for Testing the Resolution of a Raman Spectrometer