Enthalpy of the N+ + H2 → NH+ + H Reaction—Experimental Study of the Reverse Process

Abstract

The formation of nitrogen hydrides in the interstellar medium is initiated by the nearly thermoneutral reaction of N ^+ + H _2 → NH ^+ + H. Here, we experimentally determine the enthalpy of this reaction using the principle of detailed balance from a measurement of the rate coefficient of the reverse reaction NH ^+ + H → N ^+ + H _2 . The measurements were carried out in a linear radiofrequency 22-pole trap combined with an effusive beam source of atomic hydrogen at temperatures between 10 and 100 K. The resulting ground-state energy difference (or reaction enthalpy at 0 K) of Δ E ^0 = (18 ± 4) meV confirms that there are no significant energy barriers on the reaction path.

Keywords

• Astrochemistry
• Reaction rates
• Laboratory astrophysics
• Experimental data
• Molecular data
• Small molecules