Spectral induced polarization

A. Tarasov, K. Titov. (2013) On the use of the Cole-Cole equations in spectral induced polarization. Geophysical Journal International, vol. 195, pp. 352-356. 

The investigation of the complex conductivity as a function of frequency is subject of complex resistivity measurements it is called particularly in the low-frequency range (< 1000 Hz) spectral induced polarization, SIP (see Section 8.8). 

This principle of a four-electrode device is also applied for frequency-dependent measurements of the real and the imaginary rock conductivity component with the spectral induced polarization technique (see Section 8.8). In this case platinum electrodes are applied. 

Induced polarization is a current-stimulated electrical phenomenon observed as a delayed voltage response in earth materials resulting from a capacitive behaviour (Ward, 1990). This delay effect can be described and measured in the time domain and in the frequency domain. Today s spectral electrical measurements (spectral induced polarization, SIP) are state of the art. 

Binley, A., Slater, L.D., Fukes, M., Cassaini, G., 2(X)5. Relationship between spectral induced polarization and hydraulic properties of saturated and unsaturated sandstone. Water Resour. Res. 41, W12417. http //dx.doi.org/10.1029/2(X)5WR004202. 

Cassiani, G., Kemna, A., VUla, A., Zimmermann, E., 2009. Spectral induced polarization for the characterization of free-phase hydrocarbon contamination of sediments with low clay content. Near Surf. Geophys. 7, 547-562. 

Vanhala, H., 1997. Mapping oil-contaminated sand and till with the spectral induced polarization (SIP) method. Geophys. Prospect. 45, 303-326. 

Weller, A., Bdmer, F., 1996. Measurements of spectral induced polarization for environmental purposes. Environ. GeoL 27, 329-334. 

Cross-polarization in tilted frame has been proposed.275 In this scheme, the two effective fields matching the Hartmann-Hahn condition have a large offset comparable to two RF fields. This method was named SPECIFIC CP (spectrally induced filtering in combination with cross-polarization Fig. 20) because the matching depends on the resonance offset of the involved nuclei. This method is clearly useful for spectral simplification, as demonstrated in Fig. 21. Under fast spinning conditions, 7-coupling-mediated CP can be observed as shown by Verhoeven et al.216... 

When the pulses used in the experiment have finite spectral width the induced polarization in a third-order experiment is the convolution of the system... 

Finally, the SPECIFIC CP (spectrally induced filtering in combination with CP) experiment recently introduced by Baldus et al can be seen as an expansion of towards selective cross polarization. SPECIFIC applies weak RF fields and at both Larmor frequencies of a heteronuclear (Si, S2) spin system, leading to chemical shielding-dependent zero-, single- or doublequantum transfer. When neglecting CSA terms, the condition... 

Dielectric spectroscopy is similar to rheology and in many ways complementary. It especially has the advantage that it covers an extraordinary spectral range. If an electric field is applied to the sample, the induced polarization will be equal to the srmi of all molecular dipoles. In so-called A-type chains, the dipoles are parallel to the chain backbone, and, therefore, the induced polarization of each chain is proportional to its end-to-end vector R ... 

DEPT (distortionless enhancement by polarization transfer) A onedimensional C-NMR experiment commonly used for spectral editing that allows us to distinguish between CH, CH2, CH, and quaternary carbons. Detectable magnetization The magnetization processing in the x y -plane induces a signal in the receiver coil that is detected. Only single-quantum coherence is directly detectable. 

Recent work in our laboratory has shown that Fourier Transform Infrared Reflection Absorption Spectroscopy (FT-IRRAS) can be used routinely to measure vibrational spectra of a monolayer on a low area metal surface. To achieve sensitivity and resolution, a pseudo-double beam, polarization modulation technique was integrated into the FT-IR experiment. We have shown applicability of FT-IRRAS to spectral measurements of surface adsorbates in the presence of a surrounding infrared absorbing gas or liquid as well as measurements in the UHV. We now show progress toward situ measurement of thermal and hydration induced conformational changes of adsorbate structure. The design of the cell and some preliminary measurements will be discussed. 

The polar and nonpolar vapors at different concentrations were separated in PCA space. The best selectivity was obtained between toluene and DCM vapors at low concentrations, while water and ACN vapors were almost unresolved. At the highest tested vapor concentration of 0.1 P/Po, toluene and DCM vapors likely induced film swelling that resulted in the decrease in the vapor response selectivity. Overall, two first PCs described more than 98% of total variance in the spectral data with PC2 contribution of only 5% from the original spectral data. This relatively small contribution of PC2 was likely due to the film-swelling effects at high vapor concentration. 

Attention should be paid to specific interactions, which should be taken into account in the interpretation of spectral shifts in relation to the polarity of a medium. Drastic changes in the fluorescence spectrum may indeed be induced by hydrogen bonding. 

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