orthohydrogen
/ˌɔːθəʊˈhʌɪdrədʒ(ə)n/ /ˈɔːθəʊˌhʌɪdrədʒ(ə)n/Chemistry
noun
The form of molecular hydrogen whose spectrum exhibits a hyperfine structure of triplets owing to the two nuclei in the molecule having parallel spins.
- Orthohydrogen differs slightly in physical properties from the other form, parahydrogen, and forms about 75 per cent of hydrogen in equilibrium at room temperature..
Origin
1920s; earliest use found in Chemical Abstracts. From ortho- + hydrogen, after German Orthowasserstoff. Compare orthohelium, parahydrogen.