It has been known since 1927 that two modifications of hydrogen exist: para-H
2 and ortho-H
2. Pure para-H
2 can be prepared by leading a 1:3 para:ortho mixture of “normal” H
2 over a catalyst at low temperature. In 1933 Farkas and Sachsse [1] measured the rate coefficient of para-ortho H
2 conversion in gas mixtures with the paramagnetic open-shell molecules O
2, NO, and NO
2.
[more]
