What to ask for in a 222 nm excimer lamp spectrum

Two excimer lamps can both show a sharp peak at 222 nm and still produce different spectra outside it. That difference matters when a lab has to assess a finished fixture. A normalized curve helps identify the source, but a trace on a linear scale with the peak set to 100% can hide weak emissions farther from the peak. Get the underlying measurement before treating two lamps or filters as interchangeable.

Request a trace you can interpret

Ask for spectral irradiance with units, wavelength range and the instrument settings. The report should identify the lamp, driver, filter and any window in the optical path. Record the measurement distance and angle, the warm-up condition and how the lab determined its detection floor. Ask for data in a table as well as a plot. A curve that appears to go to zero is ambiguous if the report gives no detection limit.

A broadband meter can be useful for tracking a fixture that has already been characterized. For initial comparison, ask the test lab for a wavelength-resolved measurement and a description of how it controlled stray light. A strong peak can contribute stray light inside a spectroradiometer, obscuring much weaker signals. The NIST study on far-UVC filters examines how longer-wavelength emissions can affect an exposure assessment even when the peak measurement looks similar.

Identify the exact optical assembly

Put the filter part number and revision on the same line as the lamp model in the bill of materials. Keep a record of whether the spectrum was captured on the bare source, on the source with its specified filter, or on the complete fixture. A window or filter supplied by a different vendor is a reason to review the optical evidence for the new assembly.

One example is the YOYO UV SBS-222-3W compact excimer lamp. Its product page identifies the nominal 222 nm emission and says the supplied specifications leave the presence of an integrated filter unconfirmed. For a prototype build, put the filter configuration and a matching spectral report in the purchase request.

Retain the fixture measurement

Have the qualified test lab evaluate the assembled fixture in its intended geometry. Keep the wavelength-resolved data and measurement setup with the fixture revision so a replacement lamp, filter or window can be checked against the same reference. Evaluate photobiological exposure and any relevant air-quality effects for the actual installation under the applicable requirements. The component trace is evidence about the light source. Fixture release depends on the measurements and assessment for the completed system.

The primary study Exposure of Human Skin Models to KrCl Excimer Lamps gives an example of how researchers compared filtered and unfiltered spectra.

Disclosure. YOYO UV supplies the example lamp. This technical note was prepared for YOYO UV with AI assistance.