Electronic transitions of C[sub 3][sup −] above the photodetachment threshold (original) (raw)
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Electronic transition of C 3 H − in the vicinity of the lowest photodetachment threshold
Molecular Physics, 2001
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Gas-Phase Electronic Transitions of Carbon Chain Anions Coinciding with Diffuse Interstellar Bands
The Astrophysical Journal, 1998
Gas-phase electronic spectra of several carbon chain anions have been measured in the laboratory and compared with diffuse interstellar bands (DIBs). The lowest energy transition of shows seven prominent narrow bands, Ϫ C 7 five of which show striking matches with narrow DIBs while the other peaks are obscured by broader, more intense, DIBs. The origin bands in the corresponding spectra of , , and also appear to match DIBs.
Electronic Transitions Responsible for C60 + Diffuse Interstellar Bands
The Journal of Physical Chemistry Letters, 2018
Diffuse interstellar bands (DIBs) are puzzling absorption features believed to contain critical information about molecular evolution in space. Despite the fact that C 60 + recently became the first confirmed carrier of several DIBs, the nature of the corresponding transitions is not understood. Using electronic structure methods, we show that the two strong C 60 + DIBs cannot be explained by electronic transitions to the two different excited 2 E 1g states or the two spin−orbit components of the lowest 2 E 1g state, as suggested before. We argue that the strong DIBs at 9632 and 9577 Å correspond to the cold excitations from the non-Franck−Condon region of the ground electronic state to the two components of the lowest 2 E 1g state split by Jahn−Teller distortion. The weak DIBs at 9428 and 9365 Å are assigned to the first vibronic transitions involving the low-energy vibrational modes and components of the lowest 2 E 1g electronic state.
Ultraviolet Measurements of Interstellar C 2
The Astrophysical Journal, 2012
We analyzed archival spectra acquired with the Hubble Space Telescope for a study of interstellar C 2 . Absorption from the electronic transitions, D 1 Σ + u -X 1 Σ + g (0,0) as well as F 1 Π u -X 1 Σ + g (0,0) and (1,0), was the focus of the study. Our profile syntheses revealed that the lines of the F − X bands were broadened as a result of a perturbation involving the upper levels. Further evidence for the perturbation came from anomalies in line strength and position for the F − X (0,0) band. The perturbation likely arises from a combination of triplet-singlet interactions involving spin-orbit mixing between 3 Π u states and F 1 Π u and an avoided crossing between the 3 Π u states. Tunneling through a potential barrier caused by the 3 and 4 1 Π u states and spin-orbit mixing with other close-lying triplet states of ungerade symmetry are less likely. Except for the broadening, lines in the F − X (1,0) band appear free from anomalies and can be used to study interstellar C 2 ; new results for 10 sight lines are presented.
Saturation and polarization dependence of degenerate four-wave mixing on the example of C3
electronic transitions of C 3 Ϫ were observed in a neon matrix and in the gas phase, although the energy of the excited electronic states involved in these transitions is 1-1.5 eV above the photodetachment threshold. The excited Feshbach states are sufficiently long-lived that some of the bands in the gas-phase photodetachment spectrum exhibit rotational structure. Assignment of the transitions is made on the basis of rotational analysis or profile simulations and theoretical calculations. The b 4 ⌸ u ←X 2 ⌸ g transition is also weakly observed. The presence of such discrete bands, though in the continuum, provides a means of detection for anions in the interstellar medium.
Electronic spectra of carbon chain anions: C[sub 2n]H[sup −] (n=5–12)
The Journal of Chemical Physics, 1999
The electronic absorption spectra of mono-hydrogenated carbon chain anions C 2n H Ϫ (nϭ5-10͒ have been measured in the gas-phase and in 6 K neon matrices (nϭ8-12͒. The techniques of resonant two-color electron photodetachment in the gas-phase and absorption spectroscopy of mass-selected anions in neon matrix were used. A homologous series is observed, with band system origins shifting from 304 nm for C 10 H Ϫ to 590 nm for C 20 H Ϫ. In conjunction with ab initio calculations the band systems are attributed to a 1 ⌺ ϩ ←X 1 ⌺ ϩ transition of linear acetylenic anions. Another near lying electronic transition due to a second isomer is also apparent for C 10 H Ϫ up to C 24 H Ϫ. Comparison with tables of the known diffuse interstellar bands indicates possible matches for the origin bands of the C 18 H Ϫ and C 20 H Ϫ isomers.
The Astrophysical …, 2001
The electronic spectrum of the linear propadienylidene anion has been recorded at 50 K by l-C 3 H 2 resonance-enhanced two-photon detachment spectroscopy. This resembles the absorption spectrum to the dipole bound state involving bound-bound and bound-free transitions. The wavelength of the K \ 1^0 component for the origin and three vibrational bands match the weak and narrow di †use interstellar bands. To explain the abundance of this carrier in interstellar clouds, the ratio of anions to neutrals is estimated for small polar molecules with high electron affinities using chemical considerations. An appreciable amount of anions can result in di †use clouds because the electron attachment to polar molecules is enhanced via dipole bound states.
Laser excitation spectrum of C3 in the region 26000–30700cm−1
Journal of Molecular Spectroscopy, 2010
The vibrational structure of theà 1 P u electronic state of C 3 in the region 26 000-30 775 cm À1 has been reexamined, using laser excitation spectra of jet-cooled molecules. Rotational constants and vibrational energies have been determined for over 60 previously-unreported vibronic levels; a number of other levels have been reassigned. The vibrational structure is complicated by interactions between levels of the upper and lower Born-Oppenheimer components of theà 1 P u state, and by the effects of the double minimum potential in the Q 3 coordinate, recognized by Izuha and Yamanouchi [16]. The present work shows that there is also strong anharmonic resonance between the overtones of the m 1 and m 3 vibrations. For instance, the levels 2 1 + 1 and 0 1 + 3 are nearly degenerate in zero order, but as a result of the resonance they give rise to two levels 139 cm À1 apart, centered about the expected position of the 2 1 + 1 level. With these irregularities recognized, every observed vibrational level up to 30 000 cm À1 (a vibrational energy of over 5000 cm À1) can now be assigned. A R þ u vibronic level at 30181.4 cm À1 , which has a much lower B 0 rotational constant than nearby levels of theà 1 P u state, possibly represents the onset of vibronic perturbations by theB 01 D u electronic state; this state is so far unknown, but is predicted by the ab initio calculations of Ahmed et al. [36].