Evolution of multiple quantum coherences with scaled dipolar Hamiltonian.

In this article, we introduce a pulse sequence which allows the monitoring of multiple quantum coherences distribution of correlated spin states developed with scaled dipolar Hamiltonian. The pulse sequence is a modification of our previous Proportionally Refocused Loschmidt echo (PRL echo) with phase increment, in order to verify the accuracy of the weighted coherent quantum dynamics. The experiments were carried out with different scaling factors to analyze the evolution of the total magnetization, the time dependence of the multiple quantum coherence orders, and the development of correlated spins clusters.

Experimental quantification of decoherence via the Loschmidt echo in a many spin system with scaled dipolar Hamiltonians.

We performed Loschmidt echo nuclear magnetic resonance experiments to study decoherence under a scaled dipolar Hamiltonian by means of a symmetrical time-reversal pulse sequence denominated Proportionally Refocused Loschmidt (PRL) echo. The many-spin system represented by the protons in polycrystalline adamantane evolves through two steps of evolution characterized by the secular part of the dipolar Hamiltonian, scaled down with a factor |k| and opposite signs. The scaling factor can be varied continuously from 0 to 1/2, giving access to a range of complexity in the dynamics.

Parahydrogen Induced polarization by homogeneous catalysis: theory and applications.

The alignment of the nuclear spins in parahydrogen can be transferred to other molecules by a homogeneously catalyzed hydrogenation reaction resulting in dramatically enhanced NMR signals. In this chapter we introduce the involved theoretical concepts by two different approaches: the well known, intuitive population approach and the more complex but more complete density operator formalism. Furthermore, we present two interesting applications of PHIP employing homogeneous catalysis.

Long-lived 1H singlet spin states originating from para-hydrogen in Cs-symmetric molecules stored for minutes in high magnetic fields.

Nuclear magnetic resonance (NMR) is a very powerful tool in physics, chemistry, and life sciences, although limited by low sensitivity. This problem can be overcome by hyperpolarization techniques dramatically enhancing the NMR signal. However, this approach is restricted to relatively short time scales depending on the nuclear spin-lattice relaxation time T(1) in the range of seconds.

Proton magnetic resonance imaging with para-hydrogen induced polarization.

A major challenge in imaging is the detection of small amounts of molecules of interest. In the case of magnetic resonance imaging (MRI) their signals are typically concealed by the large background signal of e.g.

Quantification of H(2)O(2) concentrations in aqueous solutions by means of combined NMR and pH measurements.

The NMR transverse relaxation time T(2), determined by a CPMG multipulse sequence, of aqueous hydrogen peroxide (H(2)O(2)) solutions strongly depends on the rate of exchange of the spin-bearing protons between the H(2)O(2) and H(2)O molecules. For pulse separations exceeding the inverse exchange rate, this value becomes a constant only depending on proton exchange time and magnetic field strength. Since this exchange time depends in a non-analytical way on the concentration of H(2)O(2) and on the pH value, a measurement of T(2) and pH allows the inversion of the data for the non-invasive determination of the H(2)O(2) concentration.