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J Wasicki

Publications and source records attributed to J Wasicki.

5 recordsLinked to original sources
PubMed2004

Simple two-pulse time-reversal sequence for dipolar and quadrupolar-coupled spin systems.

We demonstrate, both theoretically and experimentally, that two-pulse sequence (2n+1) X 90 degrees(Y) - 90 degrees(X) -Acq(t) without delay between pulses, yields the reverse of time evolution of spin system with dipolar and quadrupole interactions. This process results in refocusing of the spin magnetization into magic echo at te = t1/2 after the second pulse, where t1 is the length of the first pulse.

Journal Article↗
PubMed2004

Calculation of dipolar correlation function in solids with internal mobility.

A general equation for the dipolar correlation function, to be used to analyze various kinds of independent internal motions, described by some correlation times tau(cm) (m = 1,2 em...k), has been obtained. The obtained expression has been used to analyze the temperature dependencies of different NMR measured values: second moment: spin-lattice relaxation times; amplitude of solid echoes signals.

Journal Article↗
PubMed2002

Solid echo in the slow-motion region. Effects of the finite pulse widths.

The effects of nonzero radio-frequency pulse widths on the echo signals in solids with molecular motions have been investigated. It has been shown that in the slow-motion region a time position and an amplitude of the echo signal depend not only on the width of the pulse, but also on the shape of potential wells and the correlation time, describing the molecular motion. A comparison of the developed theory with experimental results obtained for polycrystalline NH4Cl demonstrates a good agreement between them.

Ammonium Chloride↗
PubMed2000

Effect of hydrostatic pressure on N(CH3)4+ cation motion in ferroelectric N(CH3)4H(Cl3CCOO)2.

The proton spin-lattice relaxation time in ferroelectric N(CH3)4H(Cl3CCOO)2 has been studied under isobaric conditions at pressures 0.1, 200 and 400 MPa over a wide range of temperature. The data indicate that the dominant relaxation mechanism for T1 can be attributed to the classical CH3 group reorientation of N(CH3)4+ cation. The influence of pressure on methyl group reorientation of N(CH3)4+ cation was analysed.

Cations, Monovalent↗