Ion-molecule reactions at 4/sup 0/K

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1981

OSTI ID:6049546

Luine, J A

A new apparatus and technique have been developed for the measurements of reaction rates for reactions of ions with hydrogen in the temperature range 4/sup 0/ less than or equal to T approximately less than 25/sup 0/K. Ions are trapped in a static field quadrupole ion trap (Penning trap) and are immersed in a 4/sup 0/K hydrogen gas. The ion-neutral interaction temperature is varied by varying the rate at which the ion cloud uniformly rotates in the stationary neutral gas. The relative number of ions of each species as well as the ion-neutral collision rate are monitored with time and the results are analyzed to obtain the probability of reaction for an average ion-neutral collision. The reaction rate coefficient is obtained by multiplying the reaction probability by the collision rate coefficient, k/sub c/, determined by the quantum scattering theory of Arthurs and Dalgarno (1960). The technique has been demonstrated by measuring the reaction probabiilties P/sub R/(T) for the reactions N/sup +/ + H/sub 2/ ..-->.. NH/sup +/ + H, NH/sub 3//sup +/ + H/sub 2/ ..-->.. NH/sub 4//sup +/ + H, C/sup +/ + H/sub 2/ ..-->.. CH/sub 2//sup +/ + H nu, HCO/sup +/ + H/sub 2/ ..-->.. H/sub 3/CO/sup +/ + H nu, H/sub 2//sup +/ + H/sub 2/ ..-->.. H/sub 3//sup +/ + H. The N/sup +/ reaction is found to be endoergic by 0.0022 +- 0.0002 eV and its reaction probability is found to satisfy the relation P/sub R/(T) = (0.54 +- 0.27)E/sup -(24 +- 2.5)/T/ for 4/sup 0/ less than or equal to T less than or equal to 300/sup 0/K. At 4/sup 0/K, the rate coefficient is k = (2.2 +- 0.3) x 10/sup -13/cm/sup 3//s for hydrogen consisting of three parts ortho and one part para hydrogen (normal hydrogen). The NH/sub 3//sup +/ reaction probability is found to decrease with increasing temperature approximately according to T/sup -1/ /sup 4/. The result incorporated into the model of Herbst and Klemperer (1973) shows that this reaction is the most important ion-moleucle reaction leading to the production of interstellar ammonia.

• Research Organization: Colorado Univ., Boulder (USA)
• OSTI ID: 6049546
• Country of Publication: United States
• Language: English

Related Subjects

640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
ACYL RADICALS
AMMONIA
CARBON IONS
CATIONS
CHARGED PARTICLES
COLLISIONS
ELEMENTS
FORMYL RADICALS
HYDRIDES
HYDROGEN
HYDROGEN COMPOUNDS
HYDROGEN IONS
HYDROGEN IONS 2 PLUS
ION COLLISIONS
ION-MOLECULE COLLISIONS
IONS
MOLECULAR IONS
MOLECULE COLLISIONS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NITROGEN IONS
NONMETALS
PROBABILITY
RADICALS
TEMPERATURE DEPENDENCE
ULTRALOW TEMPERATURE