Solid-state experiment

Rotators in the solid state experience a well defined potential, with a depth and symmetry resulting from interactions with surrounding ions or molecules. Combined translation and rotation of CD4 lead to a much less specified meaning of the apparent activation energy obtained experimentally. Obtained values indicate that we have different values of the activation energy for different temperature ranges. Therefore their relation to local potentials at the walls of cages requires a further study. 

In the solid state experiments the protons are used to cross-polarize the carbon nuclei. Sufficient time must be allowed for the protons to thermalize with the lattice in between experiments but, unless the sample is inhomogeneous, all protons will share a... 

Nearly the same limits of r exist in real solid state experiments. However, the relevant maximal time tm which could be achieved in such computer simulations (see equation (5.1,60)) for a given Tq, could turn out to be not long enough for determining the asymptotic laws under question. For instance, existence of so-called small critical exponents in physics of phase transitions [14] was not experimentally confirmed since to obtain these critical exponents, the process covering several orders of the parameter t — fo should be... 

In this chapter, we report the results of some solid-state experiments on NaY zeolite and vanadium pentoxide, V205 (18). 

It is not surprising to us that the current CIDEP study was not able to pinpoint the role of the excited singlet reaction. Nevertheless, the results of the solid state experiments at 77 K discussed earlier support the recent CIDNP product analysis of similar lignin model reactions which strongly indicate a primary direct 0-cleavage reaction from the excited singlet state (9,11-12). 

NQR is intrinsically a solid state experiment. At 77 °K all except a very few elements and compounds are in the solid state and therefore accessible to NQR experiments as long as the substance incorporates nuclei with /> 1/2. 

Solid-state experiments use a dry sample that is packed into a rotor and spun at high frequency inside the spectrometer s magnetic field. This approach is termed cross-polarization magic angle spinning (CPMAS), and is the standard protocol for solids. It relies on transfer of magnetization from protons to C (or other nuclei) in order to achieve rapid analyses with reasonably narrow spectral lines. Cody et al. 

Electrochemical (cyclovoltametric) investigations of the ladder-type poly-(para-phenylene) species 71 support the results of the chemical oxidation (doping) experiments both in solution and in the solid state (film). A reversible oxidation takes place and it is well-separated into two waves especially in the solid-state experiment. These are assigned to the formation of radical cationic (79) and dicationic species (80), respectively. The halfwave potential (E1/2) for the first oxidation wave lies between 0.75 V (solution experiment) and 0.95 V (solid state - film) - versus a standard calomel electrode SCE) [106]. Consequently, one has to search for an alternative synthetic process to generate the ladder-type poly(phenylenemethide)s 77 or polymers containing extended segments of the fully unsaturated structure desired. The oxidation of polymeric carbanions appeared suitable, but it proved necessary to work under conditions which completely exclude water and air. 

A very useful class of solid-state experiments exploits the rotational resonance condition, where the rotation frequency is set to be equal to a multiple... 

Crini et al. used HRMAS NMR spectroscopy for exploring inclusion complexes of P-cyclodextrin with textile dye [28]. The authors performed a series of 2D solid-state experiments (NOESY, TOCSY and HSQC) to estabhsh the structure of the IC under investigation. An important contribution was achieved through the HOHAHA experiment. The results showed that, through this new NMR technique, it is possible to characterize cross-linked materials with limited mobility. 

As novel solution and solid state experiments enabling the determination of shielding tensor quantities in peptides and proteins become widespread, it is strongly recommended that practitioners stick to precise definitions of terms that have accepted meanings within the solid state NMR community. As a reminder, we list again the modern terms The difference between the most shielded (ass) and the least shielded (an) tensor component is the span. 

In addition, fewer chemically distinct types of nitrogen moieties, compared to the number of carbon moieties, in polymers should result in simpler spectra, and easier identification of resonances and their quantitative analysis. These properties of15N NMR spectra should also enable the detection of byproducts and minor products which would probably be undetected in the relatively complicated 13C spectra. However, the small gyromagnetic ratio (about 40% of that of 13C) and low natural abundance of the 15N isotope (Table 1) result in about 30 times less sensitivity compared to 13CNMR. Therefore, isotopic enrichment is usually required, particularly for solid state experiments. 

Molecular beam resonance experiments performed on CsBr and LiBr resulted in a coarse determination of the Br nuclear magnetic moments. Pound subsequently used solution-state Br NMR experiments (a negative solid-state experiment was attempted on a single crystal of KBr) to improve the precision of both magnetic moments by nearly an order of magnitude. The first bromine SSNMR spectrum ( Br) was acquired by Pound using a single crystal of NaBr. Relative to far fewer liferature reporfs confain Br SSNMR experi-... 

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