LOW TEMPERATURE PHASE TRANSITIONS IN BIPHENYL
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Date
1978
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Ohio State University
Abstract
Phase transitions have been detected in biphenyl at about $42^{\circ}\, K$ and $17^{\circ}\, K$ by noting changes in the transmitted light intensity when the crystal is placed, at extinction, between crossed polarizers and the crystal temperature slowly varied. The phase transition at $42^{\circ}\, K$ is gradual (i.e. it occurs over 3 range of temperature) while the $17^{\circ}\, K$ transition is abrupt. The effect is observed only for light propagating normal to an $a^{*} b$ section which implies that the atomic displacements at the phase transitions are largely restricted to this plane. An analogous behavior is observed for bipheny $1-d_{10}$ except that the onset of the gradual transition on cooling is $38^{\circ}\, K$ and the abrupt transition is at $24^{\circ}\,K$. Further evidence for the $17^{\circ}\, K$ phase transition has been obtained through a study of the temperature variation of the two-photon absorption origin linewidth.
Description
Author Institution: Department of Chemistry, University of British Columbia; Laboratorio Spettroscopia, Molecolare del CNR, 40126 Bologna, Italy; Ames Laboratory, Iowa State University