Using our spectroscopic technique based on molecular beam electric resonance without A and B fields [Chem. Phys. Lett. 341 (2001) 495] depletion spectra of both NO and (NO)(2) were measured. The experimental results show an energy shift of the order of 10(-8) cm(-1) between the maxima of their (central) band spectra. This resolution enables to estimate changes in the NO dipole moment of the order of 0.6%, as this molecule forms the dimer. It is suggested that this technique could be used to investigate molecular rearrangements in gas-phase dynamical processes as well as to resolve variations in molecular bond distances in solvation or cluster processes. (C) 2004 Elsevier B.V. All rights reserved.