Total cross sections for positron and electron collisions with NH3and H2O molecules

The total cross sections for 1-400 eV positrons and electrons colliding with NH 3 and H 2 O molecules were measured using a TOF method. The cross sections were obtained by a normalisation method. The results for e + -NH 3 and e + -H 2 O at low energy were much lower than the theoretical values of Jain (1986). The cross sections of positronium formation in these gases were measured.