Electron–ion recombination in nuclear recoils tracks in nonpolar liquids. Calculation of the effect of external electric field on the escape probability

• Electron recombination in nuclear recoils tracks is studied by computer simulations.
• The electron escape probability depends on the direction of applied electric field.
• Application of molecular liquids in directional dark matter detectors is discussed.

A computer simulation method is applied to study electron–ion recombination in tracks of low-energy nuclear recoils in nonpolar liquids in which the electron transport can be described as ideal diffusion. The electron escape probability is calculated as a function of applied electric field, both for the field parallel to the track and for the field perpendicular to the track. The dependence of escape probability on the field direction is the stronger, the longer the ionization track, with a significant effect being found already for tracks of ~100 nm length. The results are discussed in the context of possible applications of nonpolar molecular liquids as target media in directional dark matter detectors.