Exceptional Dispersion in DNP Crystals in the Visible Spectral Range

Abstract

In DNP monomer crystals the indicatrix, the optic axes angle, the birefringence, and the absorption tensor were measured in the VIS and NIR spectral range. A crossed-axial-plane dispersion is found with change of the plane orientation in the green region (1.9 · 10⁴ cm⁻¹) of the spectrum. Calculations of the polarizability tensor by tensorial addition of the bond polarizabilities show that the polarizabilities of the molecules only can not yield the measured orientation of the indicatrix. Polarizabilities with other orientations must be involved. Assigning polarizabilities to intermolecular contacts with short distances can explain the measured behavior.

Key Words:

• Dispersion
• DNP
• Ferroelectric
• Birefringence
• polarizability