| 释义 |
parahydrogen
(stress variable)
Also para hydrogen and with hyphen.
[f. para-1 3 + hydrogen, as tr. G. parawasserstoff (Bonhoeffer & Harteck 1929, in Naturwissenschaften XVII. 182/1), coined on the analogy of par(a)helium (see quot. 1935 s.v. orthohydrogen).]
The form of molecular hydrogen in which the two nuclei in the molecule have antiparallel spins, so that the spectrum exhibits no hyperfine structure. Cf. orthohydrogen.
1929Industr. & Engin. Chem. 10 July 6/1 At room temperatures and atmospheric pressure in glass vessels para-hydrogen is a stable gas. 1935, etc. [see orthohydrogen]. 1969H. T. Evans tr. G. Hägg's Gen. & Inorg. Chem. xviii. 452 The melting and boiling points of parahydrogen are approximately 0·1° lower than for ordinary hydrogen. |