A Measurement of Photon Production in Electron Avalanches in CF4
  This paper presents a measurement of the ratio of photon to electron production and the scintillation spectrum in a popular gas for time pro jection chambers, carbon tetrafluoride (CF4), over the range of 200 to 800 nm; the ratio is measured to be 0.34+/-0.04. This result is of particular importance for a new generation of dark matter time projection chambers with directional sensitivity which use CF4 as a fill gas. 
A. Kaboth, J. Monroe, S. Ahlen, D. Dujmic, S. Henderson, G. Kohse, R.   Lanza, M. Lewandowska, A. Roccaro, G. Sciolla, N. Sk...