We report here a laser induced transient dip in the electrical conductivity of some crude toxic samples of organic
origin prepared in liquid base. The electrical conductivity variation of the samples under laser exposure indicates to the
occurrence of phenomenon similar to Optogalvanic effect in liquid. In the Optogalvanic effect the current of a
discharging gas varies (may increase or decrease) as the discharge cavity is irradiated by a resonant electromagnetic
field. This phenomenon, which has thoroughly been investigated both theoretically and experimentally for last few
decades, has not been reported so far in liquid medium. In our work the samples in liquid base were placed between the
electrodes of a conductivity tester and their respective electrical conductivities were measured. Once the laser was
switched on in the cavity between the electrodes of the tester, the conductivity went down nearly by an amount ranging
from 0.2% to 0.5% of the original values. The dip in conductivity was temporary and disappeared as soon as the laser
source was removed.
The experimental results are being explained in the light of Optical Nutation of the dipole moments of the
molecules caused by the resonant nonlinear interaction of the molecules with the electric field of the laser. As an
extension of F. Bloch's work on nuclear induction to optical frequency, we have shown that the Nutation of the dipole
vectors of the interacting molecules cause a dephasing among them. This dephasing, which the key to our observation,
leads to a decrease in the electrical polarizability of the medium, which finally decreases the ion production rate between
the electrodes and the detector shows a dip in conductivity.