Vibrationally resolved band profiles for autoionisation of NO (c 3Π) nℓλ ( vR=0) Rydberg states into NO + A 1Π ( vi=0, 1, 2) vibronic levels

Abstract

Excitation spectra for dispersed VUV-fluorescence of NO ( λ fl=134–152 nm) were measured in the exciting-photon energy range between 16.9 and 24.8 eV using monochromatised synchrotron radiation at medium bandwidth of 29 meV. Fluorescence from A 1Π ( v i=0, 1, 2) vibronic NO +-levels and fluorescence from excited dissociation fragments NI (3s 2P J) was observed simultaneously by recording the dispersed fluorescence with a monochromator–position-sensitive detector combination. The autoionisation of NO (c 3Π) nℓλ ( v R=0) Rydberg levels into the NO + A 1Π ( v i=0, 1, 2) vibronic levels was observed vibrationally resolved. Different Beutler–Fano profiles for autoionisation of one Rydberg level NO (c 3Π) nℓλ ( v R=0) into the different vibronic NO + A 1Π ( v i=0, 1, 2) levels are clearly visible. The dependence of the Beutler–Fano profiles on the quantum numbers n, ℓ, and λ of the Rydberg electron is discussed. For the direct photoionisation into the NO + A 1Π ( v i=0, 1, 2) vibronic levels a non-Franck–Condon behaviour was observed.