نتایج جستجو برای: orthohydrogen
تعداد نتایج: 15 فیلتر نتایج به سال:
(1)H NMR signal amplification by reversible exchange (SABRE) was observed for pyridine and pyridine-d5 at 9.4 T, a field that is orders of magnitude higher than what is typically utilized to achieve the conventional low-field SABRE effect. In addition to emissive peaks for the hydrogen spins at the ortho positions of the pyridine substrate (both free and bound to the metal center), absorptive s...
Activation of a catalyst [IrCl(COD)(IMes)] (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene; COD = cyclooctadiene)] for signal amplification by reversible exchange (SABRE) was monitored by in situ hyperpolarized proton NMR at 9.4 T. During the catalyst-activation process, the COD moiety undergoes hydrogenation that leads to its complete removal from the Ir complex. A transient hydride i...
Hydrogen is an unusual substance in that its molecule exists in two forms, known as ortho and para, with markedly different properties. Energy level of the ortho molecule is higher than para, therefore, the latter is employed for industrial purposes. Consequently, for a high conversion of ortho to para hydrogen a catalyst reactor must be employed. Therefore, one of the main obj...
In situ neutron inelastic scattering experiments on hydrogen adsorbed into a fully deutrated tetrahydrofuran-water ice clathrate show that the adsorbed hydrogen has three rotational excitations (transitions between J=0 and 1 states) at approximately 14 meV in both energy gain and loss. These transitions could be unequivocally assigned since there was residual orthohydrogen at low temperatures (...
The solid parahydrogen crystal has proven to be an extraordinary matrix medium. The very weak intermolecular interaction with relatively high-zero-point lattice vibration in combination with the small mass of the molecule lead to a highly quantum system in which hydrogen molecules rapidly tunnel between equivalent sites. This tunnelling process is the basis for a powerful self-annealing behavio...
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