Space-group frequency 207 polar

N-(2-acetamido-4-nitropheryl)pyrrolidene (PAN) is dimorphic. The thermodynamically stable form is non-polar (Fig.2), (14). The crystal space group is P21 with two independent molecules per asymmetric unit which are related by a pseudo center of inversion. This crystal does not display measurable frequency doubling generation. 

Silicon is a model for the fundamental electronic and mechanical properties of Group IV crystals and the basic material for electronic device technology. Coherent optical phonons in Si revealed the ultrafast formation of renormalized quasiparticles in time-frequency space [47]. The anisotropic transient reflectivity of n-doped Si(001) featured the coherent optical phonon oscillation with a frequency of 15.3 THz, when the [110] crystalline axis was parallel to the pump polarization (Fig. 2.11). Rotation of the sample by 45° led to disappearance of the coherent oscillation, which confirmed the ISRS generation,... 

The appropriate spacing of groups in the polymer so that maximum bonding can occur, especially to ionic and polar groups on the keratin structure, is also important to substantivity. As a first approximation, the maximum frequency of primary bonds and the maximum molecular size will provide maximum substantivity. 

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