Emission from a doped crystal with structural changes under pulse heating of the sample

The parameters of radiation emitted by an anthracene-doped biphenyl crystal are studied in the temperature range from 5.5 to 40 K at different densities of excitation power W by the third harmonic of an Nd laser. The doublet structure of the induced emission spectum is attributed to the emission from commensurate and incommensurate phases of the crystal. The anomalous behavior of the frequency interval Δν between the doublet lines is explained by structural changes of the matrix in the region of the incommensurate phase II. A decrease in Δν upon an increase in W is associated with sample heating. The specific heat of the crystal under investigation is determined experimentally with a laser excitation under the assumption of thermodynamic equilibrium. The difference between the obtained value of heat capacity and the one measured calorimetrically is explained by using the hypothesis of generation of excess phonons upon laser excitation due to peculiarities of relaxation processes (or the “phonon bottleneck” type).

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