An experimental study of radiation-induced pure dephasing: ArF excited emission of O2

Abstract

The effects of incoherent incident light on both nonresonant and resonant secondary radiation (RSR) are demonstrated for the spontaneous emission of O2. ArF excimer radiation (FWHH∼120 cm−1) is resonant with several rovibronic features of the v′=4 band of the Schumann–Runge absorption system. Off-resonant contributions to the RSR spectrum are Raman-like (v″=1) but carry the linewidth of the incident incoherent radiation. Purely resonant emission features are found to be entirely fluorescence-like (v″≥6). Other RSR vibrational bands of O2 exhibit contributions of both types of emission including interferences between Raman (off-resonant) and fluorescence (resonant) amplitudes. The observed depolarization ratios also reflect these various emission characters. The RSR spectra of O2 excited by incoherent (ArF) driving fields are contrasted with that due to monochromatic excitation. Convolution of the incident spectral density with a rovibronic Kramers–Heisenberg irreducible tensor treatment of resonance Raman scattering cross sections is shown to capture all the observed RSR emission characteristics.