Abstract:Accurate ab initio calculations have been performed in order to investigate both the stable isomers and the reactivity of the N(2)H(2)(+) cation. In addition to the trans-HNNH(+) isomer already observed in the photoelectron studies, a formaldehyde type (isodiazene cation) and H(2)O(2)-like isomers are found. At the coupled cluster level of theory, the isodiazene cation is calculated to be as stable as trans-HNNH(+). We have also studied the reactivity of N(2)H(2)(+) and its implication on the reactive processe… Show more
“…The present calculations, in agreement with earlier lower-level studies by Pople and Curtiss, indicate that there are three local minima on the ground-state PES. Recent RCCSD[T] calculations by Palaudoux and Hochlaf suggest that the cis structure is actually a saddle point and that two other nonplanar minima exist on the ground-state surface. 3 CCSD(T)/TZ2P(f,d) geometries of the iso -, cis -, and trans -diazene cations.…”
Two series of small polyatomic ions, HxCO+ and HxN2+ (x = 1, 2, 3), were systematically characterized using three correlated theoretical techniques: density functional theory using the B3LYP functional, spinrestricted second-order perturbation theory, and singles + doubles coupled cluster theory with perturbative triples. On the basis of thermodynamic data, the existence of these ions in inductively coupled plasma mass spectrometry (ICP-MS) experiments is not surprising since the ions are predicted to be considerably more stable than their corresponding dissociation products (by 30−170 kcal/mol). While each pair of isoelectronic ions exhibit very similar thermodynamic and kinetic characteristics, there are significant differences within each series. While the mechanism for dissociation of the larger ions occurs through hydrogen abstraction, the triatomic ions (HCO+ and HN2+) appear to dissociate by proton abstraction. These differing mechanisms help to explain large differences in the abundances of HN2+ and HCO+ observed in ICP-MS experiments.
Disciplines
Chemistry
CommentsReprinted (adapted) ReceiVed: September 7, 2007; In Final Form: January 4, 2008 Two series of small polyatomic ions, H x CO + and H x N 2 + (x ) 1, 2, 3), were systematically characterized using three correlated theoretical techniques: density functional theory using the B3LYP functional, spinrestricted second-order perturbation theory, and singles + doubles coupled cluster theory with perturbative triples. On the basis of thermodynamic data, the existence of these ions in inductively coupled plasma mass spectrometry (ICP-MS) experiments is not surprising since the ions are predicted to be considerably more stable than their corresponding dissociation products (by 30-170 kcal/mol). While each pair of isoelectronic ions exhibit very similar thermodynamic and kinetic characteristics, there are significant differences within each series. While the mechanism for dissociation of the larger ions occurs through hydrogen abstraction, the triatomic ions (HCO + and HN 2 + ) appear to dissociate by proton abstraction. These differing mechanisms help to explain large differences in the abundances of HN 2 + and HCO + observed in ICP-MS experiments.
“…The present calculations, in agreement with earlier lower-level studies by Pople and Curtiss, indicate that there are three local minima on the ground-state PES. Recent RCCSD[T] calculations by Palaudoux and Hochlaf suggest that the cis structure is actually a saddle point and that two other nonplanar minima exist on the ground-state surface. 3 CCSD(T)/TZ2P(f,d) geometries of the iso -, cis -, and trans -diazene cations.…”
Two series of small polyatomic ions, HxCO+ and HxN2+ (x = 1, 2, 3), were systematically characterized using three correlated theoretical techniques: density functional theory using the B3LYP functional, spinrestricted second-order perturbation theory, and singles + doubles coupled cluster theory with perturbative triples. On the basis of thermodynamic data, the existence of these ions in inductively coupled plasma mass spectrometry (ICP-MS) experiments is not surprising since the ions are predicted to be considerably more stable than their corresponding dissociation products (by 30−170 kcal/mol). While each pair of isoelectronic ions exhibit very similar thermodynamic and kinetic characteristics, there are significant differences within each series. While the mechanism for dissociation of the larger ions occurs through hydrogen abstraction, the triatomic ions (HCO+ and HN2+) appear to dissociate by proton abstraction. These differing mechanisms help to explain large differences in the abundances of HN2+ and HCO+ observed in ICP-MS experiments.
Disciplines
Chemistry
CommentsReprinted (adapted) ReceiVed: September 7, 2007; In Final Form: January 4, 2008 Two series of small polyatomic ions, H x CO + and H x N 2 + (x ) 1, 2, 3), were systematically characterized using three correlated theoretical techniques: density functional theory using the B3LYP functional, spinrestricted second-order perturbation theory, and singles + doubles coupled cluster theory with perturbative triples. On the basis of thermodynamic data, the existence of these ions in inductively coupled plasma mass spectrometry (ICP-MS) experiments is not surprising since the ions are predicted to be considerably more stable than their corresponding dissociation products (by 30-170 kcal/mol). While each pair of isoelectronic ions exhibit very similar thermodynamic and kinetic characteristics, there are significant differences within each series. While the mechanism for dissociation of the larger ions occurs through hydrogen abstraction, the triatomic ions (HCO + and HN 2 + ) appear to dissociate by proton abstraction. These differing mechanisms help to explain large differences in the abundances of HN 2 + and HCO + observed in ICP-MS experiments.
“…They are used in the atmospheric models, neglecting, hence, reactants carrying internal energy. 6 However, recent experimental findings 7,8 and theoretical calculations [9][10][11][12][13][14] have demonstrated the importance of both electronically and vibrationally excited reactants on this sort of reactions, especially, the branching ratios are affected. Accordingly, the consideration of the reactivity on the electronic excited states in the models dedicated to planetary atmospheres has been suggested.…”
Accurate ab initio calculations are performed to investigate the stable isomers of [MgO(3)](+) and its lowest electronic states at both molecular and asymptotic regions. The calculations are done using large basis sets and configuration interaction methods including the complete active space self-consistent field, the internally contracted multi-reference configuration interaction, the standard coupled cluster (RCCSD(T)) approaches and the newly implemented explicitly correlated coupled cluster method (RCCSD(T)-F12). The presence of three stable forms is predicted: a cyclic global minimum c-MgO(3)(+), which is followed by a quasi-linear isomer, l2-MgO(3)(+). A third isomer of C(s) symmetry (l1-MgO(3)(+)) is also found. Moreover, we computed the one-dimensional cuts of the six-dimensional potential energy surfaces of the lowest doublet and quartet electronic states of [MgO(3)](+) along the R(MgO) and R(OO) stretching coordinates covering both the molecular and the asymptotic regions. These curves are used later for discussing the metastability of this cation and to propose plausible mechanisms for the Mg(+) + O(3) atmospherically important ion-molecule reaction and related reactive channels.
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