  The interaction of strong pulsed femtosecond laser field with atoms having
three equivalent electrons in the outer shell ($p^3$ configuration, e.g.
nitrogen) is studied via numerical integration of a time-dependent
Schr\"{o}dinger equation on a grid approach. Single, double and triple
ionization yields originating from a completely antisymmetric wave function are
calculated and extracted using a restricted-geometry model with the soft-core
potential and three active electrons. The direct triple ionization channel is
found to produce a larger yield than the channel connected with single and then
direct double ionization. Compared against earlier results investigating the $n
s^ 2 n p^1$ configuration, we propose that the differences found here might in
fact be accessible through electron's momentum distribution.
