High-accuracy measurement of the emission spectrum of liquid xenon in the vacuum ultraviolet region

The emission spectrum of cryogenic liquid xenon in the vacuum ultraviolet region was measured by irradiating liquid xenon with gamma-rays from a radioactive source. To achieve a high signal-to-noise ratio, we employed coincident photon counting. Additionally, the charge of the photo-sensor signals was measured to estimate the number of detected photons accurately. In addition, proper corrections were incorporated for the wavelength; response functions of the apparatus obtained using a low-pressure mercury lamp, and photon detection efficiencies of the optical system were considered. The obtained emission spectrum is found to be in the shape of a Gaussian function, with the center at 57,199±34 (stat.)±33 (syst.)cm−1 (174.8±0.1 (stat.)±0.1 (syst.)nm) and the full width at half maximum of 3328±72 (stat.)±65 (syst.)cm−1 (10.2±0.2 (stat.)±0.2 (sys.)nm). These results are the most accurate values obtained in terms of the data acquisition method and the calibration for the experimental system and provide valuable information regarding the high-precision instruments that employ a liquid-xenon scintillator.