Near-infrared absorption spectra of 16O3 and 18O3: Adiabatic energy of the 1A2 state?

Abstract

New absorption spectra of the ¹A₂(0,v₂,1)←¹A₁(0,0,0) bands of ¹⁶O₃ and ¹⁸O₃ near 1 μ are reported. The behavior of vibronic band isotope shifts for low v₂ suggests that the lowest point on the ¹A₂ surface lies 9990±70 cm⁻¹ above the ¹A₁ minimum. This result is relatively insensitive to the vibrational assignment. Accounting for zero‐point and binding energies of the ground state places the ¹A₂ minimum very close to the O+O₂(v=0) dissociation limit, not low enough to support the zero‐point energy of a bound state. Implications regarding recent speculation on the role of this and other electronically excited states in ozone photochemistry are discussed.