Quantum-chemical investigations of small molecular anions

Botschwina, Peter; Seeger, S.; Mladenović, Mirjana; Schulz, Bernd; Horn, Matthias; Schmatz, Stefan; Flügge, J.; Oswald, Rainer

doi:10.1080/01442359509353308

Cited by 46 publications

(30 citation statements)

References 127 publications

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“…11,12 For the odd-numbered carbon anions, C 2nϩ1 Ϫ , nϭ1 -4, theoretical studies predicted linear equilibrium structures, corresponding to ... g 2 u 2 g(u) 4 u(g) 1 2 ⌸ u(g) ground states. [13][14][15][16][17] The observed transitions in the visible-UV range were assigned to states produced by the promotion of an electron from valence and orbitals to the highest occupied orbital. For C 3 Ϫ the lowest energy ← promotions give rise to long lived Feshbach resonant states at energies above the electron affinity of the neutral.…”

Section: Introductionmentioning

confidence: 99%

Theoretical and experimental study of the A2Πu–X2Πg band system of C7−

Lakin

Tulej

Maier

et al. 2000

The Journal of Chemical Physics

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The A 2 ⌸ u -X 2 ⌸ g electronic system of gaseous C 7Ϫ is examined experimentally in the light of theoretical predictions. Ab initio calculations at the RHF, RCCSD͑T͒ and MRCI levels using the aug-cc-pVQZ basis set indicate that the transition is accompanied by a small elongation in the molecule and a significant reduction in the spin-orbit coupling constant. On the basis of these predictions the band profiles of the 0 0 0 , 1 0 1 , 2 0 1 and 3 0 1 transitions were recorded using photodetachment spectroscopy. These spectra revealed the spin-orbit component bands for each transition as well as providing band contours which show partially resolved rotational structure. The experimental spectra are compared to simulations based upon the calculated spectroscopic constants and the possible causes of the main features in the band contours are accessed by least-squares fitting of the profiles for the 0 0 0 and 1 0 1 transitions. The implications for the recent observation of coincidences between the A 2 ⌸ u -X 2 ⌸ g vibronic bands of C 7Ϫ and the diffuse interstellar bands are discussed.

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Section: Introductionmentioning

confidence: 99%

Theoretical and experimental study of the A2Πu–X2Πg band system of C7−

Lakin

Tulej

Maier

et al. 2000

The Journal of Chemical Physics

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“…Their electric dipole moments are 3.1 and 0.65 Debye, respectively (Brünken et al 2007b;Botschwina et al 1995).…”

Section: Observations and Identification Of Cn −mentioning

confidence: 99%

Astronomical identification of CN^-, the smallest observed molecular anion

Agúndez¹,

Cernicharo

Guèlin³

et al. 2010

A&A

228

179

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We present the first astronomical detection of a diatomic negative ion, the cyanide anion CN − , and quantum mechanical calculations of the excitation of this anion by means of collisions with para-H 2 . The anion CN − is identified by observing the J = 2−1 and J = 3−2 rotational transitions in the C-star envelope IRC +10216 with the IRAM 30-m telescope. The U-shaped line profiles indicate that CN − , like the large anion C 6 H − , is formed in the outer regions of the envelope. Chemical and excitation model calculations suggest that this species forms from the reaction of large carbon anions with N atoms, rather than from the radiative attachment of an electron to CN, as is the case for large molecular anions. The unexpectedly high abundance derived for CN − , 0.25% relative to CN, indicates that its detection in other astronomical sources is likely. A parallel search for the small anion C 2 H − remains inconclusive, despite the previous tentative identification of the J = 1−0 rotational transition. The abundance of C 2 H − in IRC +10216 is found to be vanishingly small, <0.0014% relative to C 2 H.

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“…Botschwina and co-workers are one of the few research groups performing anharmonic FCF calculations in this way. 22,23 Recently, details of a few other types of anharmonic FCF methods have been published. [24][25][26][27][28] The major application of FCF calculations is in spectral simulation.…”

Section: Introductionmentioning

confidence: 99%

A new method of calculation of Franck–Condon factors which includes allowance for anharmonicity and the Duschinsky effect: Simulation of the He I photoelectron spectrum of ClO2

Mok

Lee

Chau

et al. 2000

The Journal of Chemical Physics

106

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A new method of Franck-Condon ͑FC͒ factor calculation for nonlinear polyatomics, which includes anharmonicity and Duschinsky rotation, is reported. Watson's Hamiltonian is employed in this method with multidimensional ab initio potential energy functions. The anharmonic vibrational wave functions are expressed as linear combinations of the products of harmonic oscillator functions. The Duschinsky effect, which arises from the rotation of the normal modes of the two electronic states involved in the electronic transition, is formulated in Cartesian coordinates, as was done previously in an earlier harmonic FC model. This new anharmonic FC method was applied to the simulation of the bands in the He I photoelectron ͑PE͒ spectrum of ClO 2 . For the first band, the harmonic FC model was shown to be inadequate but the anharmonic FC simulation gave a much-improved agreement with the observed spectrum. The experimentally derived geometry of the X 1 A 1 state of ClO 2 ϩ was obtained, for the first time, via the iterative FC analysis procedure ͕R(Cl-O͒ϭ1.414Ϯ0.002 Å, ЄO-Cl-Oϭ121.8Ϯ0.1°͖. The heavily overlapped second PE band of ClO 2 , corresponding to ionization to five cationic states, was simulated using the anharmonic FC code. The main vibrational features observed in the experimental spectrum were adequately accounted for in the simulated spectrum. The spectral simulation reported here supports one of the two sets of published assignments for this band, which was based on multireference configuration interaction ͑MRCI͒ calculations. In addition, with the aid of the simulated envelopes, a set of adiabatic ͑and vertical͒ ionization energies to all five cationic states involved in this PE band, more reliable than previously reported, has been derived. This led also to a reanalysis of the photoabsorption spectrum of ClO 2 .

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Quantum-chemical investigations of small molecular anions

Cited by 46 publications

References 127 publications

Theoretical and experimental study of the A2Πu–X2Πg band system of C7−

Theoretical and experimental study of the A2Πu–X2Πg band system of C7−

Astronomical identification of CN^-, the smallest observed molecular anion

A new method of calculation of Franck–Condon factors which includes allowance for anharmonicity and the Duschinsky effect: Simulation of the He I photoelectron spectrum of ClO2

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Quantum-chemical investigations of small molecular anions

Cited by 46 publications

References 127 publications

Theoretical and experimental study of the A2Πu–X2Πg band system of C7−

Theoretical and experimental study of the A2Πu–X2Πg band system of C7−

Astronomical identification of CN-, the smallest observed molecular anion

A new method of calculation of Franck–Condon factors which includes allowance for anharmonicity and the Duschinsky effect: Simulation of the He I photoelectron spectrum of ClO2

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Astronomical identification of CN^-, the smallest observed molecular anion