Studies of a polystyrene wavenumber standard for infrared spectrophotometry

Standard Reference Material (SRM) 1921 is a matte finish polystyrene film available from NIST for use in calibrating the wavenumber scale of spectrometers in the infrared spectral region from 515 cm(-1) to 3082 cm(-1). New results of the dependence of the calibrated peak values on measurement resolution and peak determination method are presented. Appropriate zero filling of the interferogram was found to significantly decrease peak value dependence on resolution. For any resolution less than or equal to 4 cm(-1), as determined by the center of gravity method, the peak values differ by amounts less than 0.01 cm(-1), the least significant digit of the calibration values specified in Ref. [2]. A method of extrapolating the peak minimum for an absorption band in the transmission spectrum was carried out through a chi square fit on a series of peak values obtained at different peak fractions of the same band. The extrapolated minimum peak values are presented for the first three bands of polystyrene.