Electronic Transition of Ferrocenium: Neon Matrix and CASPT2 Studies

Electronic absorptions of ferrocenium starting at 632.5 nm were measured in a 6 K neon matrix following mass-selective deposition of the ions. The spectrum shows clear vibrational structure and provides the best-yet resolved view of the electronic states of this cation. The absorption system is identified as the 1 2E1′ ← X 2E2′ transition (D5h symmmetry) on the basis of vertical excitation energies and oscillator strengths calculated at the CASPT2 level. Vibrational bands in the spectrum are assigned with the aid of the ground-state frequencies calculated with the DFT method

Electronic Spectrum of Dihydrogenated Buckminsterfullerene in a 6 K Neon Matrix

Vibrationally resolved electronic absorption spectrum of 1,2-dihydrogenated[60]fullerene has been recorded in a 6 K neon matrix after mass-selected deposition of m/z = 722 cations produced from reaction of protonated methane and C60 in an ion source. One system has the origin band at 688.5 ± 0.1 nm and another commencing at 404.8 ± 0.1 nm. Theoretical computations were used to calculate the relative energies of three isomers of dihydrogenated[60]fullerene and time-dependent density functional theory predicted the vertical excitations to 50 electronic states

Oscillatory biquadratic coupling in Fe/Cr/Fe(001)

Copyright © 1997 The American Physical SocietyPolar Kerr measurements have been used to measure the dependence of the biquadratic coupling strength B12 on Cr thickness in an Fe/Cr/Fe trilayer. The overall behavior, which consists of a maximum coupling strength at dCr=5 Å (3.5 ML) with a falloff at greater Cr thicknesses, is found to be consistent with in-plane Kerr and Brillouin light-scattering measurements performed on the same sample. The polar Kerr measurements suggest additionally that B12 increases from zero near zero Cr thickness, and that it oscillates in magnitude after the first peak, with a second peak in B12 occurring at about dCr=12 Å (8.3 ML). The positions and heights of the first and second biquadratic coupling maxima, in relation to the first bilinear coupling maximum, show excellent agreement with previous measurements by Köbler et al. of the biquadratic coupling behavior in Fe/Cr/Fe, and also show good agreement with the predictions of an intrinsic biquadratic coupling mechanism due to Edwards et al

Structure of C6HF+ and C6F2+ fragment ions from fluorobenzenes : electronic spectra in 6 K neon matrices

The fragment ions C6HF+ and C6F2+ produced from fluorobenzenes in a discharge source were trapped in 6 K neon matrices after mass selection. A strong absorption system is detected in the visible range starting at 586.3 nm for C6HF+ and 569.3 nm for C6F2+. Vibrationally resolved fluorescence commencing at the same wavelengths is observed upon laser excitation into each absorption band of these cations. The absorptions are assigned to the A2Πg ← X2Πu and A2Π ← X2Π transitions of linear FC6F+ and HC6F+, respectively. The assignment is based on the similarity of the absorption and fluorescence spectra with the A2Πg ← X2Πu electronic system of linear HC6H+ as well as the theoretically calculated vibrational and electronic excitation energies of the FC6F+ and HC6F+

The C̃2B3u ← X̃2B2g electronic absorption spectrum of butatriene cation in a neon matrix

The 2B3u ← 2B2g electronic absorption of butatriene cation (BT+) has been observed in a 6 K neon matrix. The origin band lies at 511.9 nm. The electronic transition assignment is based on comparison with the photoelectron spectrum of butatriene and the vibrational frequencies of BT+ calculated with the CASPT2 (5, 6) method. Three vibrational modes of energy 207, 511 and 813 cm−1, with their overtones and combinations, are active in the 2B3u state of BT+. It is shown that the emission observed from a glow discharge of 2-butyne at 491 nm and attributed to the origin band of this electronic transition [1] of BT+ is due to another species, because the difference of 850 cm−1 to the absorption spectrum is too large. No fluorescence of BT+ was detected in the matrix and it is expected that the 2B3u electronic state relaxes non-radiatively on a fs time scale

Electronic spectra of chloro- and bromotriacetylene cations in neon matrices

Mass-selected, chlorinated (ClC6Cl+, HC6Cl+) and brominated (BrC6Br+, HC6Br+) derivatives of triacetylene cation produced from polyhalogenated benzenes in a hot-cathode discharge source were trapped in 6 K neon matrices. Absorption is detected with onset at 710.8 nm for BrC6Br+, 655.9 nm for HC6Br+, 649.1 nm for ClC6Cl+ and 624.0 nm for HC6Cl+. Radiative decay from the v'  =  0 level of the excited electronic state is observed on laser excitation of the transition. The systems are assigned to the à 2Πg ←  2Πu electronic transition of ClC6Cl+ and BrC6Br+, and à 2Π ←  2Π of HC6Cl+ and HC6Br+. A weaker system commencing at 495.4 nm for BrC6Br+, 574.5 nm for HC6Br+, 519.9 nm for ClC6Cl+ and 499.5 nm for HC6Cl+ is present. This is due to excitation to the 2Πg/- electronic state of the halogenated triacetylene cations. The assignment is based on calculated vertical excitations energies, vibrational frequencies and similarities in the absorption and fluorescence spectra to the 2Πg, à 2Πg ←  2Πu electronic systems of triacetylene cation