  Absolute cross sections are measured for charge-exchange, ionization, and
excitation within the same experimental setup for the Li$^{+}-$Ar, K$^{+}-$ Ar,
and Na$^{+}-$ He collisions in the ion energy range $0.5-10$ keV. Results of
our measurements along with existing experimental data and the schematic
correlation diagrams are used to analyze and determine the mechanisms for these
processes. The experimental results show that the charge-exchange processes are
realized with high probabilities and electrons are predominately captured in
ground states. The cross section ratio for charge exchange, ionization and
excitation processes roughly attains the value $10:2:1$, respectively. The
contributions of various partial inelastic channels to the total ionization
cross sections are estimated and a primary mechanism for the process is
defined. The energy-loss spectrum, in addition, is applied to estimate the
relative contribution of different inelastic channels and to determine the
mechanisms for the ionization and for some excitation processes of Ar resonance
lines for the K$^{+}-$Ar collision system. The excitation function for the
helium, as well as for the sodium doublet lines for the Na$^{+}-$He collision
system, reveals some unexpected features and a mechanism to explain this
observation is suggested.
