Rotational envelope simulations in photodetachment spectroscopy: Precise measurement of electron affinity of NO and O2

Abstract

The slow-electron velocity-map imaging (SEVI) technique can achieve accuracy better than 0.1 meV for atomic electron affinity (EA) determinations. However, molecular photoelectron energy spectra frequently exhibit complex rotational fine structures that induce substantial spectral congestions, thereby compromising the precision of molecular EA measurements. To obtain precise EA values of molecular species, we implement rotational envelope simulations of photoelectron energy spectra of molecular anions. Benchmark simulations for the well-characterized OH− successfully reproduce our cryogenic SEVI experimental spectra. Through application of this methodology to NO− and O2−, we establish EA(NO) = 0.029 24(46) eV and EA(O2) = 0.4477(10) eV, markedly enhancing the precision of these fundamental parameters compared to previous determinations.