Thermal hysteresis in a lead nitrate Pb(NO3)2 crystal with cubic symmetry was studied by using both electric and thermal measurements. A appreciable temperature variation was observed in the temperature region between 240 and 300K. However, electric, elastic, X-ray Debye temperature, thermal properties, and Raman scattering measurements found no evidence for structural transitions from 80 to 575K. The previous Raman spectra for lead nitrate were observed only at 80, 300, and 485K. To clarify unknown characteristic features concerning the dynamics of both lattice vibrations and molecules in the Pb(NO3)2 single crystal, Raman scattering study was carried out in the temperature region from 200 to 300K by the micro-Raman technique. The single crystal was grown in an aqueous solution of lead nitrate by the slow evaporation method at ð313:2{312:5Þ 0:5K in 456 h. The Raman-scattering measurements were performed in the back scattering configuration at the sample growth surface. The experimental procedures were given in ref. 10. The 532 nm line of the Nd:YVO4 laser was focused on a spot with diameter of 2 mm on the sample surface. The damage caused to the sample by the incident laser beam was not observed during the measurement. The thickness of the sample is 0:095 5 cm. The temperature was controlled to within 0:1K and the spectral resolution was set to about 2 cm . The observed spectra were fitted to a Lorentzian line shape. Frequencies, line-width, and the integrated intensities of the observed peaks were obtained by a least square method. The direction of an incident laser beam is parallel to the crystallographic C3 axis such that the electric field of the incident beam is parallel to the molecular plane of the nitrate ion. The centrosymmetric structure of Pb(NO3)2 is space group T h with four molecular units per primitive cell. According to group theoretical analysis, there are 105 fundamental vibrations divided into 48 internal vibrations and 57 external vibrations. A typical Raman spectrum in the wide frequency region was shown in Fig. 1 at room temperature. The 1 and 4 internal modes of nitrate ion are clearly observed. The forbidden 2 2 mode appeared in the Raman spectrum because of a non-linear effect. The Raman spectra of lattice modes are shown in Fig. 2 as a function of temperature in the frequency regions from 40 to 200 cm . Figure 3 also shows the temperature dependence of the 1 internal mode from 1030 to 1070 cm . The observed peaks were well fitted to the Lorentzian function. The peak positions of the lattice mode and the internal 1 mode are given in Figs. 4(a) and 4(b), respectively. The temperature dependence of full width at half maximum (abbreviated as FWHM) for these modes is shown in Fig. 5. As seen in these figures, the peak positions and widths of both the internal and lattice modes show a monotonical temperature dependence. That is, no anomalous behavior 0 50