dark hydrogen

From being a state of matter which neither transmits nor reflects visible light, but can transmit infrared.

dark hydrogen (uncountable)

1. (physics) A state of hydrogen that is poorly electrically conductive (much less conductive than metallic hydrogen).
   • 2000, F. Combes, G. Pineau des Forets, Molecular Hydrogen in Space, →ISBN, page 48:

     One particular species of these candidates seems to be not dark at all: so-called dark hydrogen masses located in the optical Galactic disk.

   • 2007, Florentin Smarandache, V. Christianto, Hadron models and related New Energy issues, →ISBN, page 96:

     The over-unity energy production could be due to a gradual transformation of hydrogen to dark hydrogen in the same state as in water.

   • 2013, Tokio Ohta, Solar-Hydrogen Energy Systems, →ISBN:

     However, the rates of dark hydrogen production were relatively low.

• metallic hydrogen