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Polystyrene Mid Infrared Wavelength Reference


Polystyrene film has been a popular wavelength reference for mid-infrared spectrometers for many years. These new NIST-traceable Starna Reference Materials can be used to qualify Mid IR - FTIR spectrophotometers for wavelength accuracy over the range 3.2 µm to 18.5 µm (3125 cm-1 to 540 cm-1). Traceable to NIST SRM 1921b, 14 certified peaks are available for wavelength qualification purposes in the mid infrared. Approximate peak wavelength values are: 539, 842, 907, 1028, 1069, 1155, 1583,1601, 1943, 2849, 3001, 3026, 3060, and 3082 cm-1. Actual values are given in the calibration certificate supplied with the reference.

In addition, eight peaks, traceable to NIST SRM 2065, can be used for wavelength qualification in the near infrared. Approximate peak wavelength values are: cm-1 3064 3647 4039 4250 4335 4608 5952 8749 nm 3264 2742 2476 2353 2307 2170 1680 1143

The instrument to be qualified should have a wavenumber resolution of 2 cm-1 or better. Scan the filter over its usable range and identify the peaks whose wavelength values are given in the calibration certificate. Compare the measured values to the certificate values. Taking the expanded uncertainty budget† of the references into consideration, then the wavelength values should fall within the expected parameters† of your instrument if it is working correctly. The results may be used to build up a data log of the instrument’s wavelength accuracy over time. This may be used for certification purposes and for troubleshooting should the correlation change. The data will also be useful to a service technician to diagnose and correct any problems that may develop with your instrument.