Electronic absorption spectra of linear carbon chains in neon matrices. II. C−2n, C2n, and C2nH

Abstract

Absorption spectra observed between 400 and 2500 nm in 5 K neon matrices have been assigned to electronic transitions of linear C−2n (n=2–10): 2Π←X 2Π, C2n (n=3–7): 3Σ−u←X 3Σ−g, and C2nH (n=3–8): 2Π←X 2Π chains. The species have been produced by mass selected deposition of cations or anions produced in a hot cathode discharge source (C2n, C−2n, C2nH) and by laser vaporization of graphite (C2n, C−2n). In addition to experimental and chemical evidence, the dependence of the absorption wavelength on the number of carbon atoms was used to assign the electronic transitions. Infrared absorptions which were recorded around 2000 cm−1 are attributed to asymmetric stretching frequencies of C8, C10, and C12. This is based on correlation of their intensities with the identified electronic bands. The possible relevance of the electronic spectra of these carbon chains to astrophysical observations of diffuse interstellar bands is discussed.

Higher energy electronic transitions of HC2n+1H+ (n=2–7) and HC2n+1H (n=4–7) in neon matrices

“…If one plots the wavelength of the origin band of the strong transition of HC 2n+1 H + in the visible range as a function of the number of carbon atoms, a linear dependence is observed, as has been noted for the à 2 ⌸ b ← X 2 ⌸ a transition and for other carbon chains. 31,32 The band at 547.2 nm of HC 11 H + departs considerably from this linear plot. This suggests that it is not the onset of the C transition.…”

Electronic structure calculations on the C4 cluster

“…In Table II, the vertical excitation energies calculated in the present paper are compared with the experimental values. The papers of Maier and co-workers [12][13][14][15][16] provide low vertical energies for the lowest states. Generally, our MRCI vertical excitation energies agree relatively well with the experimental T 0 determinations of Refs.…”

“…For r-C 4 , Mühlhäuser et al 11 have located several singlet states in the 0 -5 eV internal energy range. Experimentally, numerous accurate data on these electronic states have been published by Maier and co-workers [12][13][14][15][16] and Jungen and Xu 17 using photoelectron spectroscopy and by the absorption spectra of C 4 in cold matrices. Xu et al 18 reported vertical excitation energies for l-C 4 from photoelectron spectroscopy and ab initio calculations.…”

C6H and C6D: Electronic spectra and Renner-Teller analysis

“…Refs. 10 and 11), it became possible to record the electronic spectra of C 6 H, [12][13][14][15] among many other carbon chain radicals. In a combined microwave and optical study 16 the rotationally fully resolved origin band spectra of the B 2 -X 2 electronic system of C 6 H and C 6 D were analyzed, resulting in accurate spectroscopic parameters for both 2 states.…”