Dephasing Decay of the Vibrons in Ar_x(N₂)_1−x Mixed Crystals

Abstract

In the low temperature a phase of solid N₂, vibrational excitations on individual ¹⁴N₂ molecules couple to form delocalized states with an excitonic character, the so-called vibron states. This coupling wipes away small differences in local site energy, thereby reducing the inhomogeneous line broadening. Line width measurements of the ¹⁴N₂ vibrons and the isolated ¹⁵N₂ stretching vibrations in α-(¹⁵N₂) _x (¹⁴N₂)_−x mixed crystals [1] showed that also the homogeneous linewidth is reduced for the vibron states. For increasing temperatures, the vibrational coupling among the individual molecules is destroyed [1] by scattering on librational motions which become more important towards the α-β phase transition.