We report a novel approach for determining the sign of permanent dipole moments, using nitric oxide [NO(v=0)] as an example. State-selected NO (j=|m|=|Omega=1/2) molecules are focused using a hexapole and oriented in a strong dc electric field. The angular distributions of ionic fragments resulting from extreme ultraviolet single-photon and multiphoton dissociative ionization at 400 and 800 nm are measured and indicate that the dipole moment is negative (corresponding to N-O+). The experiments thus rule out an error in the sign of the dipole of NO as the possible source of a remarkable discrepancy between previous theoretical and experimental work on orientation effects in bimolecular collisions involving oriented NO.

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Persistent URL dx.doi.org/10.1103/PhysRevLett.99.213003
Journal Phys. Rev. Lett.
Gijsbertsen, A, Siu, W, Kling, M. F, Johnsson, P, Jansen, P, Stolte, S, & Vrakking, M. J. J. (2007). Direct determination of the sign of the NO dipole moment. Phys.Rev.Lett., 99(Article number: 213003), 1–4. doi:10.1103/PhysRevLett.99.213003