Practice question

Vacuum UV refers to wavelengths so energetic that atmospheric oxygen, nitrogen and water vapor absorb strongly, necessitating evacuated optical paths and special detectors. It generally spans below approximately 190 nm down to about 10 nm, where σ→σ* transitions of single bonds and high-energy n→σ* transitions occur with very high molar absorptivity. Standard glass and quartz cuvettes as well as air-filled spectrometers cannot transmit in this region. Fluoride optics, synchrotron sources and purged chambers are required. Biological macromolecules show intense peptide absorption here, but routine assays avoid vacuum UV due to technical constraints, using near UV instead.