A study of the reactions of Ni and NiO ions relevant to planetary upper atmospheres

The reactions between Ni + ( 2 D) and O 3 , O 2 , N 2 , CO 2 and H 2 O were studied at 294 K using the pulsed laser ablation at 532 nm of a nickel metal target in a fast flow tube, with mass spectrometric detection of Ni + and NiO + . The rate coefficient for the reaction of Ni + with O 3 is k (294 K) = (9.7 ± 2.1) × 10 −10 cm 3 molecule −1 s −1 ; the reaction proceeds at the ion-permanent dipole enhanced Langevin capture rate with a predicted T −0.16 dependence. Electronic structure theory calculations were combined with Rice-Ramsperger-Kassel-Markus theory to extrapolate the measured recombination rate coefficients to the temperature and pressure conditions of planetary upper atmospheres. The following low-pressure limiting rate coefficients were obtained for T = 120-400 K and He bath gas (in cm 6 molecule −2 s −1 , uncertainty ± σ at 180 K): log 10 ( k , Ni + + N 2 ) = −27.5009 + 1.0667log 10 ( T ) − 0.74741(log 10 ( T )) 2 , σ = 29%; log 10 ( k , Ni + + O 2 ) = −27.8098 + 1.3065log 10 ( T ) − 0.81136(log 10 ( T )) 2 , σ = 32%; log 10 ( k , Ni + + CO 2 ) = −29.805 + 4.2282log 10 ( T ) − 1.4303(log 10 ( T )) 2 , σ = 28%; log 10 ( k , Ni + + H 2 O) = −24.318 + 0.20448log 10 ( T ) − 0.66676(log 10 ( T )) 2 , σ = 28%). Other rate coefficients measured (at 294 K, in cm 3 molecule −1 s −1 ) were: k (NiO + + O) = (1.7 ± 1.2) × 10 −10 ; k (NiO + + CO) = (7.4 ± 1.3) × 10 −11 ; k (NiO + + O 3 ) = (2.7 ± 1.0) × 10 −10 with (29 ± 21)% forming Ni + as opposed to NiO 2 + ; k (NiO 2 + + O 3 ) = (2.9 ± 1.4) × 10 −10 , with (16 ± 9)% forming NiO + as opposed to ONiO 2 + ; and k (Ni + ·N 2 + O) = (7 ± 4) × 10 −12 . The chemistry of Ni + and NiO + in the upper atmospheres of Earth and Mars is then discussed. The reactions between Ni + and O 3 , O 2 , N 2 , CO 2 and H 2 O; NiO + and O, O 3 and CO; and NiO 2 + and O 3 were studied at 294 K using the pulsed laser ablation of a nickel metal target in a fast flow tube, with mass spectrometric detection of Ni + and NiO + .