A study of recombination of para- and ortho-H3 + ions with electrons in an afterglow plasma is presented. A cavity ring down spectrometer was used to probe the evolutions of number densities of the lowest rotational states of the vibrational ground state of H3 + ion.
The measurement was realized at 195 K and at the pressure of helium buffer gas in the range 200-1500 Pa. Preliminary results are in good agreement with theoretical calculations.