To evaluate the feasibility of the recently proposed detection scheme of low energy neutrinos released from the Sun and supernovae called CLEAN, Cryogenic Low Energy Astrophysics with Noble Gases, which relies on the transparency of noble-gas cryogenic liquids to VUV radiation produced by neutrinos, we analyze theoretically VUV emission, self-absorption, and scattering of liquid helium and neon, primary candidates for CLEAN. Owing to strong repulsion of noble-gas atoms in the ground states at the equilibrium distance of the relevant excited state, the emission spectrum is substantially shifted from the absorption spectrum, and in principle the absorption is expected very small, allowing building large detectors. Our analysis, however, shows that the self-absorption and Rayleigh scattering are comparable to the size of the proposed detector.Our theoretical emission spectra are found in agreement with experimental observations although some deviation exists due to binary-interaction approximation, and our ab initio Rayleigh scattering lengths are found in agreement with other calculations based on the extrapolation of experimental refraction indices. The absorption process can result in either re-emission, which conserves the number of photons but delays their escape from the liquid, or in non-radiative quenching. Recently, McKinsey and Doyle [1] has proposed the detection of low energy neutrinos released from the Sun and supernovae with the scheme called CLEAN, Cryogenic Low Energy Astrophysics with Noble Gases. The central element of a CLEAN detector is a 6-meter diameter Dewar filled with liquid neon which is functioning both as a passive shielding medium and an active selfshielding detector. The advantage of liquid neon is high scintillation yield and low radiactive background. Other noble-gas liquids can be used as well, of particular interest is liquid helium. The self-absorption and scattering of UV light produced by these liquids are critical for determination of the size of the detector, the interpretation of neutrino events, and exclusion of background events. The emission of liquid helium and neon in UV has already been studied [2,3,4] and scattering lengths of noble-gas liquids at scintillation wavelengths has been estimated from extrapolations of refraction indices [5]; the self-absorption is yet to be measured. Because there are many factors such as spectral reshaping and the effects of impurities (for example, 0.2% of N 2 impurities in liquid helium reduces the emission intensity by 20-40% in the region 700-850Å [2]) that influence the interpretation of the experimental results, the theoretical calculations of emission, self-absorption, and scattering, which constitute the subject of this letter, are important. Spectral properties of noble-gas liquids are not well understood mostly due to interdisciplinary nature (atomic, molecular, condensed-matter physics) of the phenomenon as well as the scarcity of the data, so this paper also has the aim of attracting the attention of theorists of diverse exper...