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New electronic structure calculations for the transition-state region of the lowest ozone potential energy surface are reported. A two-dimensional potential energy surface in the asymptotic channel is calculated with the O2 bond distance being fixed. The calculations are performed at the multireference average quadratic coupled cluster level of theory using full-valence complete active space self-consistent field wave functions and the augmented correlation consistent polarized V6Z atomic basis set. The general shape of the potential energy surface as predicted in earlier studies, that is, a narrow transition state below the O+O2 asymptote, is confirmed by the present calculations. The transition state is 181 cm-1 below the asymptote and 72 cm-1 above the van der Waals–like minimum. The changes in the O+O2→O3* capture cross section and rate constant when the new potential energy surface is employed are investigated by means of classical trajectory calculations. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We discuss the vibrational spectrum of rotationless cyclic ozone, i.e., ozone in the so-called ring minimum of the ground electronic state. The bound state calculations utilize the ab initio potential energy surface constructed by Siebert et al. on the basis of high-level electronic structure calculations [J. Chem. Phys. 116, 9749 (2002)]. The spectrum is qualitatively similar to that of H[SUP+,SUB3], except that the energy spacing between the states belonging to the same polyad [ν[SUB1], ν[SUB2]] is much smaller; ν[SUB1] is the breathing mode and ν[SUB2] is the doubly degenerate bending mode. [ABSTRACT FROM AUTHOR]

We present an ab initio potential energy surface for the ground electronic state of ozone. It is global, i.e., it covers the three identical C[sub 2v] (open) minima, the D[sub 3h] (ring) minimum, as well as the O([sup 3]P) + O[sub 2]([sup 3]σ[sup -, sub g]) dissociation threshold. The electronic structure calculations are performed at the multireference configuration interaction level with complete active space self-consistent-field reference functions and correlation consistent polarized quadruple zeta atomic basis functions. Two of the O-O bond distances, R[sub 1] and R[sub 2], and the O-O-O bending angle are varied on a regular grid (ca. 5000 points with R[sub 1]≥R[sub 2]). An analytical representation is obtained by a three-dimensional cubic spline. The calculated potential energy surface has a tiny dissociation barrier and a shallow van der Waals minimum in the exit channel. The ring minimum is separated from the three open minima by a high potential barrier and therefore presumably does not influence the low-temperature kinetics. The dissociation energy is reproduced up to 90% of the experimental value. All bound states of nonrotating ozone up to more than 99% of the dissociation energy are calculated using the filter diagonalization technique and employing Jacobi coordinates. The three lowest transition energies for [sup 16]O[sub 3] are 1101.9 cm[sup -1] (1103.14 cm[sup -1]), 698.5 cm[sup -1] (700.93 cm[sup -1]), and 1043.9 cm[sup -1] (1042.14 cm[sup -1]) for the symmetric stretch, the bending, and the antisymmetric stretch modes, respectively; the numbers in parentheses are the experimental values. The root-mean-square error for all measured transition energies for [sup 16]O[sub 3] is only 5 cm[sup -1]. The comparison is equally favorable for all other isotopomers, for which experimental frequencies are available. The assignment is made in terms of normal modes, despite the observation that with increasing energy an increasing number of states... [ABSTRACT FROM AUTHOR]

The predissociation dynamics in the A˜ [sup 1]A[sup ″] electronic state of HNO is investigated. The quantum mechanical dynamics calculations take into account the Renner–Teller (or electronic Coriolis) coupling with the electronic ground state X˜ [sup 1]A[sup ′], which appears to be the dominant decay mechanism for the quasi-bound vibrational states in the A˜ [sup 1]A[sup ″] upper state. All three internal vibrational degrees of freedom are incorporated and two ab initio potential energy surfaces are used. The linewidths, Γ, are directly calculated by the filter diagonalization method and an absorbing optical potential in the exit channel. They are generally small (∼1 cm[sup -1]) and increase with excitation of the bending mode (bent-to-bent transition). On average, Γ increases with K, the a-axis rotational quantum number. However, for some vibrational states the linewidth shows a non-monotonic behavior with K, which is the result of mixing with highly excited vibrational levels in the continuum of the ground electronic state. This effect is even more striking, when the total angular momentum quantum number J is varied: In some cases, the linewidth exhibits a pronounced resonancelike behavior as function of J. The agreement with recent experimental spectroscopic data is satisfactory. The calculated linewidths are of the same order (within a factor of 2 or so) as the experimental ones. However, because the two ab initio potential energy surfaces do not reproduce sufficiently well the X˜–A˜ excitation energies, the resonancelike effects are not quantitatively described. Potential energy surfaces with considerably higher accuracy are required. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have performed new electronic structure calculations for the five lowest 1A′ states of ozone using the multi-reference configuration interaction method with an augmented triple zeta valence atomic basis set. Several avoided crossings, which are important for interpreting the Huggins–Hartley band system, are identified and two-dimensional diabatic potential energy surfaces are constructed. It is argued that the Huggins and the Hartley band systems are due to excitation of the same electronic state. [Copyright &y& Elsevier]

We have calculated one-dimensional potential cuts of twenty-five singlet/triplet A′/A″ states of ozone. The calculations are performed at the multi-reference configuration interaction level of electronic structure theory with the aug-cc-pVTZ set of atomic basis functions. It is found that many triplet potentials cross the 31A′(1B2) potential, on which the fragmentation after excitation in the Huggins–Hartley band system primarily proceeds. These crossings allow the population of the three spin-forbidden product channels O(3P)+O2(a1Δg), O(3P)+O2(b1Σg+) and O(1D)+O2(X3Σg−). Possible consequences of singlet–triplet crossings for the Wulf band are also briefly discussed. [Copyright &y& Elsevier]