Mass analysis studies were performed of ions detected after (2 + n) REMPI of acetylene for resonance excitations to various gerade Rydberg states as a function of laser power. These data, along with STQN/DFT calculations for dissociation of acetylene to C-2 + H-2, allowed an estimate of a threshold for photodissociation via gerade Rydberg states near 75000-77000 cm(-1). Mechanisms are proposed regarding (2 + 3) REMPI of acetylene to form C-2(+) as well as C+ and H+. Simulation analysis of partly-resolved rotational structured spectra recorded for different jet cooling allowed determinations of precise spectroscopic parameters and lifetime estimates for the Rydberg state, 4p(1)Delta(g)0(0). (C) 2008 Elsevier B.V. All rights reserved.