Two-photon transitions between the perturbed 6<i>s</i><sup>2</sup> <sup>1</sup><i>S</i><sub>0</sub> ground state and the perturbed 5<i>d</i>7<i>s</i><sup>3</sup><i>D</i><sub>2</sub> state of a Ba atom have been experimentally investigated with different perturbing and exciting radiations. A strong dependence of the
probability of two-photon transitions between these perturbed states on the mutual orientation of the electric vectors of
the exciting and perturbing radiations has been found.
At three-photon ionization of aligned Ba atoms by radiation of laser on color centers (8300 - 9100 cm<SUP>-1</SUP>) resonant maxima caused by two-photon excitation of bound states were observed. Moreover, maxima which can't be explained by known processes were also observed.
The new unknown resonances which occur in the case of multiphoton ionization of Ba atoms at simultaneous influence of two laser fields were discovered. The character of the display of these resonances depends on mutual orientation of polarization vectors of these fields.