Kinetic Study of the Reaction Ca⁺ + N₂O from 188 to 1207 K

Abstract

Ion-molecule reactions involving metallic species play a central role in the chemistry of planetary ionospheres and in many combustion processes. The kinetics of the Ca(+) + N(2)O --> CaO(+) + N(2) reaction was studied by the pulsed multiphoton dissociation at 193 nm of organo-calcium vapor in the presence of N(2)O, followed by time-resolved laser-induced fluorescence spectroscopy of Ca(+) at 393.37 nm (4(2)P(3/2) <-- 4(2)S(1/2)). This yielded k(188-1207 K) = 5.45 x 10(-11) (T/300 K)(0.53) exp(282 K/T) cm(3) molecule(-1) s(-1), with an estimated accuracy of +/-13% (188-600 K) and +/-27% (600-1207 K). The temperature dependence of this barrierless reaction, with a minimum in the rate coefficient between 400 and 600 K, appears to be explained by the role of N(2)O vibrational excitation. This is examined using a classical trajectory treatment on a potential energy surface calculated at the B3LYP/6-311+g(2d,p) level of theory.

Design and characterization of a linear quadrupole ion trap for high-resolution Coulomb-crystal time-of-flight mass spectrometry

“…To stop the reaction, we closed the leak valve and unblocked the 397 nm laser again to recrystallize the Coulomb crystal prior to its ejection into the TOF spectrometer. From this experiment, we determined a second order rate constant for the reaction of Ca + with N 2 O of 5.49(32) · 10 −11 cm 3 s −1 which agrees with the value reported by Spears and Fehsenfeld [33] but is a factor of 2.4 to 2.9 lower than the values reported by Plane et al and Lavrov et al [32,34]. It should be emphasized, however, that because of the slight temperature dependence of this reaction and the non-thermal conditions prevailing in our experiment (the ions are not in thermal equilibrium because of their micromotion [6]), the comparison of our rate constant with the room-temperature values from the literature can only be approximate.…”

“…The second order rate constant calculated from this data is k = 4.2(10) · 10 −10 cm 3 s −1 which is a factor of 3 to 10 larger than other values reported in the literature for this reaction at room temperature [32][33][34]. The error quoted for our value of k represents the uncertainty of the fit to the experimental data.…”

“…Figure 4b shows measured low-resolution time-of-flight (TOF) spectra of mixed species Coulomb crystals consisting of Ca + , CaO + and CaOH + ions at different DC offsets applied to the extraction meshes. CaO + ions were created by leaking N 2 O into the chamber to react with Ca + in the reaction Ca + + N 2 O → CaO + + N 2 [32][33][34]. CaOH + was formed from Ca + reacting with water which was introduced into the vacuum chamber as a contamination of the N 2 O gas.…”

Metal ion-molecule kinetics at combustion temperatures: The reaction of Ca+ with O2

“…Two essentially simultaneous studies with this technique have now been made. The rate coefficients of the exothermic bimolecular Ca + + N2O reaction showed a small positive T-dependence from 600 to 1200 K [24]. The rate coefficients of the present Ca + + O2 + Ar reaction have a negative T-dependence similar to that of the equivalent reaction of neutral atoms of K, the element preceding Ca in the periodic table.…”

Short-Lived Trace Gases in the Surface Ocean and the Atmosphere

“…In the past 5 years there has been active laboratory research on IO, OIO, IONO 2 and the higher iodine oxides (I 2 O x , x ¼ 2-5) (Dillon et al 2008;Gómez Martín et al 2009;Gravestock et al 2005;Joseph et al 2007; Kaltsoyannis and Plane 2008;Plane et al 2006). Figure 1.5 is a schematic diagram of our current understanding of tropospheric iodine chemistry.…”