Fourteen ions (Ar+, Ar-2(+), ArH+, H2O+, H+(H2O), H+(H2O)(2), O+, O-2(+), OH+, NO+, N-2(+), N+, Ar-2(+), N-4(+)) were detected, by mass-resolved ion-energy measurements when the discharge was operated at 50W and fluxes of 2.5 and 5.0 slm. The crucial role of three molecular ions (Ar-2(+), ArH+, H2O+) during the radial contraction, from diffuse (r = (750 +/- 50) mu m) to contracted plasma jet (r = (500 +/- 50) mu m), and the relationship between power, gas flow and molecular ions production were pointed out. Ion energy distributions for Ar-2(+), ArH+ and H2O+ exhibit their maxima at high-energies due to low-energy threshold for three-body collision reactions. (C) 2014 Elsevier B.V. All rights reserved.