Reassignment of the vibrational structure of the Huggins absorption band of ozone

Comparison of the Huggins band for six ozone isotopologues: vibrational levels and absorption cross section

By use of the 3(1)A' ab initio potential energy surface (PES) of ozone and the multi-configuration time-dependent Hartree program for wavepacket propagation, we have determined numerous eigenstates of this state for six ozone isotopologues. These bound vibrational levels are the upper levels of the Huggins band, which covers the range from 27,000 to ~33,000 cm(-1). This study extends our previous work on the Hartley band, which was limited to the range ~32,000-50,000 cm(-1). Four isotopologues, (16)O(3), (16)O(17)O(16)O, (16)O(18)O(16)O, and (18)O(3) (noted hereafter 666, 676, 686, and 888), are symmetric, and two are asymmetric, (17)O(16)O(2) and (18)O(16)O(2) (noted hereafter 667 and 668). The PES of the 3(1)A' state has two equivalent minima of C(s) symmetry located at ~27,000 cm(-1) above the X(1)A(1) ground state. The equilibrium geometry of these two minima is r(e(1)) = 2.28 a(0), r(e(2)) = 3.2 a(0), and θ(e) = 107°. The dissociation limit of this PES, which correlates to the O((1)D) + O(2) ((1)Δ) "singlet" channel, is about 4300 cm(-1) above the two minima. For the (16)O(3) isotopologue, the 120 lowest bound eigenstates have been calculated and partially assigned up to 800 cm(-1) below the dissociation limit. The 60 lower eigenstates are easily assignable in term of three normal modes, the "long" bond (ν(1)), the bending (ν(2)), and the "short" bond (ν(3)). A new family of wave functions, aligned along the dissociation channels, appears at 3782 cm(-1) above the 3(1)A' (0,0,0) level. The 3(1)A' vibrational levels and the corresponding intensity factors from the (000), (010), (100), and (001) levels of the X(1)A(1) ground state have been calculated for the six isotopologues. The Huggins absorption cross sections of the six isotopologues have been calculated from the 3(1)A' vibrational energy levels and the corresponding intensity factors. The rotational envelope of each vibronic band has been empirically described by an ad hoc function. The ratio of the Huggins cross section of each ozone isotopologue with one of (16)O(3) provides the fractionation factor of each ozone isotopologue as a function of the photon energy. These various fractionation factors will allow predicting enrichments due to photolysis by various light sources like the actinic flux.

The Huggins band of ozone: A theoretical analysis

The Huggins band of ozone is investigated by means of dynamics calculations using a new (diabatic) potential energy surface for the 3 (1)A'(1B2) state. The good overall agreement of the calculated spectrum of vibrational energies and intensities with the experimental spectrum, especially at low to intermediate excitation energies, is considered as evidence that the Huggins band is due to the two C(s) potential wells of the 1B2 state rather than the single C2v well of the 2 (1)A'(1A1) state. The vibrational assignment of the "cold bands," based on the nodal structure of wave functions, on the whole supports the most recent experimental assignment [J. Chem. Phys. 115, 9311 (2001)]. The quantum mechanical spectrum is analyzed in terms of classical periodic orbits and the structure of the classical phase space.

The Huggins band of ozone: Unambiguous electronic and vibrational assignment

The Huggins band of ozone is investigated by means of exact dynamics calculations using a new (diabatic) potential energy surface for the (1)B(2) state. The remarkable agreement with the measured spectrum strongly suggests that the Huggins band is due to the two C(s) potential wells of the (1)B(2) state. The vibrational assignment, based on the nodal structure of wave functions, supports the most recent experimental assignment.