In spite of the fact that inversion is a symmetry operation of both the crystalline and the magnetic lattice of NiO, second harmonic generation (SHG) has been observed below the Néel temperature. A spectroscopic study shows that the signal is due to combined magnetic-dipole and electric-dipole transitions between the (3d)(8) levels of the Ni(2+) ion in the crystal field. The SHG is resonant in both the incoming and the outgoing light waves and thus greatly enhanced. A quadratic coupling of the nonlinear polarization to the order parameter was found. This allows the investigation of individual domains.
Dielectric loss spectra covering 13 decades in frequency were collected for 2-ethyl-1-hexanol, a monohydroxy alcohol that exhibits a prominent Debye-like relaxation, typical for several classes of hydrogen-bonded liquids. The thermal variation of the dielectric absorption amplitude agrees well with that of the hydrogen-bond equilibrium population, experimentally mapped out using near infrared (NIR) and nuclear magnetic resonance (NMR) measurements. Despite this agreement, temperature-jump NIR spectroscopy reveals that the hydrogen-bond switching rate does not define the frequency position of the prominent absorption peak. This contrasts with widespread notions and models based thereon, but is consistent with a recent approach.
In this section the algorithmic language EULER is described first informally and then formally by its syntax and semantics. An attempt has been made to generalize and extend some of the concepts of ALGOL, thus creating a language which is simpler and yet more flexible than ALGOL 60. A second objective in developing this language was to show that a useful programming language which can be processed with reasonable efficiency can be defined in rigorous formality.
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