Lamp characterization

An AvaSpec‐ULS4096CL‐EVO spectrometer (Avantes Inc., Louisville, CO) calibrated to measure absolute irradiance was used to obtain the irradiance spectra. The normalized spectral irradiance for the KrCl lamp alone and with the addition of a filter is shown in Fig. 1. The spectral irradiance of the filtered KrCl lamp was plotted by multiplying the unfiltered KrCl spectrum by the transmission of the custom filter. This approach for obtaining the filtered KrCl spectrum was required because the addition of a filter to the KrCl lamp decreased the emissions outside of the 222 nm peak below detectable levels for the spectrometer. In addition to the radiometrically calibrated spectrometer, a calibrated Hamamatsu UV Power Meter (C9536/H9535‐222, Hamamatsu Photonics K.K., Japan) was also used to verify the irradiance values during exposures. Exposures for the unfiltered KrCl lamp were performed with an irradiance of 0.85 mW cm⁻², and exposures with the filtered KrCl lamp used an irradiance of 0.59 mW cm⁻². The irradiance of the low‐pressure mercury lamp was 0.24 mW cm⁻².

Plot of the spectral irradiance of a KrCl lamp normalized to the 222 nm peak (–). Also plotted is the normalized spectral irradiance of the KrCl lamp with the addition of a custom filter that reduces the intensity outside of the 222 nm peak (+).