Analysis of Low-Lying Gerade Rydberg States of Acetylene Using Two-Photon Resonance Fluorescence Excitation Spectroscopy

Abstract

The np gerade Rydberg states of acetylene were analyzed using two-photon resonance fluorescence excitation spectroscopy in the 72,000-93,000 cm(-1) energy region. The npπ(1)Σ(g)(+) and npπ(1)Δ(g) Rydberg series (n = 3-5) were identified in the fluorescence excitation spectrum measured by monitoring the C(2) d(3)Π(g)-a(3)Π(u) Swan system. Some vibronic bands were assigned to the npπ(1)Δ(g)-X̃(1)Σ(g)(+) transition on the basis of rotational analysis. The 5pσ(1)Π(g) state was observed, which is the first such observation in an npσ(1)Π(g) series. Rotational analysis of the 5pσ(1)Π(g)-X̃(1)Σ(g)(+) transition showed e/f-symmetry dependent predissociation of acetylene in the 5pσ(1)Π(g) state. The 0(0)(0) band of the deuterated acetylene (C(2)D(2)) 4pπ(1)Σ(g)(+)-X̃(1)Σ(g)(+) transition exhibits an atypical structure, which was satisfactorily reproduced by a simple model of quantum interference between the discrete and quasi-continuum states. The predissociative lifetimes of the npπgerade Rydberg states were estimated from the spectral profiles. The predissociation mechanism of acetylene in the Rydberg states is discussed.

Generalized oscillator strengths of low-lying electronic excitations in acetylene

“…For example, the photoabsorption spectra in the vacuum ultraviolet (VUV) region have been extensively studied both experimentally [7][8][9][10][11][12] and theoretically [12][13][14][15][16][17][18], and detailed assignments have been made for the transition bands of the molecule. Besides, the optically-forbidden states have also been explored by means of electron energy loss spectroscopy (EELS) [19][20][21][22] and resonance enhanced multiphoton ionization (REMPI) spectroscopy [23][24][25][26]. In addition to the spectroscopic information, the absolute photoabsorption and electron scattering cross sections have received considerable interest due to their importance in modeling related astrophysical phenomena and plasma processes.…”

Excited states of aurocarbons: CASPT2 and CCSD(T) calculations of C2Au2 and C2Au4

“…Valence and Rydberg excited states of acetylene, the parent molecule of diauroacetylene, have been a subject of numerous detailed theoretical and experimental investigations, see, for example, Ventura et al [32], Wetmore and Schaefer [51], Malsch et al [52], Bowman and Miller [53], Dressler and Allan [54], Tsuji et al [55], Hammond et al [56], Demoulin and Jungen [57], Perić et al [58], Patterson et al [59], and Watanabe and Takahashi [60]…”

“…Numerous theoretical investigations on valence, Rydberg and valence/Rydberg mixed excited states of ethylene, including [26–70] offer deep insight into the understanding of (not easy) basic features of experimental electronic spectra of ethylene. In Table 6, we present results of our CASPT2 calculations in comparison with selected theoretical and experimental data from literature.…”

“…Dressler and Allan [54], Tsuji et al [55], Hammond et al [56], Demoulin and Jungen [57], Peri c et al [58], Patterson et al [59], and Watanabe and Takahashi [60] Much attention was paid to the geometry optimization of excited states [32,51,[61][62][63] with the conclusion that the geometry of the first triplet excited state of C 2 H 2 is the cis 3 B 2 state which correlates with the linear 3 Σ þ u state. Vertical excitation energies of low-lying electronic states obtained with methods applied in the present work and selected literature data are compared in Table 2.…”