Experimente �ber Para- und Orthowasserstoff

Selective hyperpolarization of heteronuclear singlet states via pulsed microtesla SABRE

“…Signal Amplification By Reversible Exchange, [1][2][3][4][5][6] or SABRE, is a nonhydrogenative variant of Para-Hydrogen Induced Polarization (PHIP) 7,8 that derives hyperpolarization from reversible interactions of substrates with parahydrogen, the readily prepared singlet spin isomer of dihydrogen, via association with an iridium catalyst. [9][10][11][12] SABRE has a distinct advantage over other hyperpolarization techniques because the polarization source is prepared as a singlet. This allows one to directly transfer the p-H 2 singlet order onto target spin pairs and store their hyperpolarization in a singlet state at any magnetic field (Table I).…”

Determination of the Interval between the Ground States of Para- and Ortho- H2

“…H 2 , for instance, exists in two distinct nuclear-spin forms, called nuclear-spin isomers, with parallel (I ¼ 1, ortho-H 2 ) or antiparallel (I ¼ 0, para-H 2 ) proton spins. The para isomer can be isolated and stored in large amounts [7].…”

Dissociative recombination of H3+and D5+

“…Heisenberg had in 1927 predicted that H 2 should exist in two different forms, ortho-hydrogen in which the nuclear spins are aligned in the same direction, and para-hydrogen with opposite nuclear spins, and the ortho/para ratio should be 3 : 1 [12]. In his nomination of Heisenberg for the physics prize, dated 31 January 1930, Svedberg pointed out that Heisenberg's prediction of the allotropic forms of hydrogen, as Svedberg phrased it, had now been experimentally verified [13,14]. Svedberg argued that this was the very important experimental discovery, predicted by the new atomic theory, that the physicists were looking for.…”