Femtosecond pulses (790 nm) are used for nonresonant laser excitation of superfluid liquid helium to prepare ionic and neutral excited states at energies above 18 eV. Measurements of laser-induced fluorescence and photocurrent enable a detailed description of the primary photoprocesses. A controllable excitation regime unique to femtosecond pulses is realized at laser intensities below the dielectric breakdown threshold, I < 5 X 10(13) W/cm(2). A steady state of the long-lived triplet excimers He-2*((3)a) (lowest Rydberg state) is established; the concentration decays between laser pulses through diffusion-controlled bimolecular annihilation to similar to 10(12) cm(-3) at a laser repetition rate of 500 Hz. The triplet population is amplified with each pulse in a sequence that involves: (1) ionization of the Rydberg electron of He-2* via complete Coulomb barrier suppression; (2) cascade electron impact ionization of the ground-state He atoms by the ponderomotively accelerated quasifree electrons in liquid He; (3) localization and thermalization of the "hot＇＇ electrons and He+ cations to form electron "bubble＇＇ and He-3(+) "snowball＇＇ states; (4) recombination of these elementary charge carriers to form He-2*. The amplification factor for the triplets M = 2(m) characterizes the excitation sequence: m is the number of generations in the cascade (m = 5 at I = 4.5 X 10(13) W/cm(2)), and m is proportional to the laser intensity and temporal pulse width. The laser-induced ionization cascade prepares an inhomogeneous initial distribution of spatially separated ions on three length scales: clumps of positive charges with an interionic separation determined by the cascade length of 60 Angstrom; a cloud of electrons surrounding the clump at the electron thermalization length similar to 10(3) Angstrom; and interclump separation dictated by the concentration of the He-2* precursors, similar to 10(4) Angstrom.