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Sunahori FX, Smith TC, Clouthier DJ. Spectroscopic identification and characterization of the aluminum methylene (AlCH 2) free radical. J Chem Phys 2022; 157:044301. [DOI: 10.1063/5.0101060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The AlCH2 free radical has been spectroscopically identified for the first time. This highly reactive species was produced in an electric discharge jet using trimethylaluminum vapor in high pressure argon as the precursor. The laser-induced fluorescence spectrum of the [Formula: see text] band system in the 513–483 nm region was recorded, and the 0–0 bands of AlCH2 and AlCD2 were studied at high resolution. The fine structure splittings were found to be due primarily to the Fermi contact interaction in the excited state rather than the usual spin–rotation coupling. Rotational analysis gave the molecular constants of the combining states, and the geometries were obtained as [Formula: see text] and [Formula: see text]. The bond lengths correspond to an aluminum–carbon single bond in both states.
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Affiliation(s)
- Fumie X. Sunahori
- Department of Chemistry and Biochemistry, Rose-Hulman Institute of Technology, 5500 Wabash Ave., Terre Haute, Indiana 47803, USA
| | - Tony C. Smith
- Ideal Vacuum Products, LLC, 5910 Midway Park Blvd. NE, Albuquerque, New Mexico 87109, USA
| | - Dennis J. Clouthier
- Ideal Vacuum Products, LLC, 5910 Midway Park Blvd. NE, Albuquerque, New Mexico 87109, USA
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Tarroni R, Clouthier DJ. Ab initio spectroscopy of the aluminum methylene (AlCH 2) free radical. J Chem Phys 2020; 153:014301. [PMID: 32640824 DOI: 10.1063/5.0010552] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Extensive ab initio investigations of the ground and electronic excited states of the AlCH2 free radical have been carried out in order to predict the spectroscopic properties of this, as yet, undetected species. Difficulties with erratic predictions of the ground state vibrational frequencies, both in the literature and in the present work, have been traced to serious broken-symmetry instabilities in the unrestricted Hartree-Fock orbitals at the ground state equilibrium geometry. The use of restricted open-shell Hartree-Fock or complete active space self consistent field orbitals avoids these problems and leads to consistent and realistic sets of vibrational frequencies for the ground state. Using the internally contracted multireference configuration interaction method with aug-cc-pV(T+d)Z basis sets, we have calculated the geometries, energies, dipole moments, and vibrational frequencies of eight electronic states of AlCH2 and AlCD2. In addition, we have generated Franck-Condon simulations of the expected vibronic structure of the Ã-X̃, B̃-X̃, C̃-X̃, and C̃-Ã band systems, which will be useful in searches for the electronic spectra of the radical. We have also simulated the expected rotational structure of the 0-0 absorption bands of these transitions at modest resolution under supersonic expansion cooled conditions. Our conclusion is that if AlCH2 can be generated in sufficient concentrations in the gas phase, it is most likely detectable through the B̃2A2-X̃2B1 or C̃2A1-X̃2B1 electronic transitions at 515 nm and 372 nm, respectively. Both band systems have vibrational and rotational signatures, even at modest resolution, that are diagnostic of the aluminum methylene free radical.
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Affiliation(s)
- Riccardo Tarroni
- Dipartimento di Chimica Industriale "Toso Montanari," Università di Bologna, Viale Risorgimento 4, 40136 Bologna, Italy
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Aerts A, Brown A. A revised nuclear quadrupole moment for aluminum: Theoretical nuclear quadrupole coupling constants of aluminum compounds. J Chem Phys 2019; 150:224302. [PMID: 31202232 DOI: 10.1063/1.5097151] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The nuclear quadrupole moment of aluminum (27Al) has been re-evaluated by determining the electric field gradients at this nucleus for AlF and AlCl using the coupled cluster method with single, double, and perturbative triple excitations [CCSD(T)]/aug-cc-pwCVXZ (X = T and Q) accounting for both vibrational averaging and core-core/core-valence electron correlation and then comparing to the experimentally measured nuclear quadrupole coupling constants (NQCCs). The new recommended value is Q(27Al) = 148.2 ± 0.5 mb, which can be compared to the previous value of 146.6 ± 1 mb. Using the new value of the nuclear quadrupole moment, the accuracy is assessed for several computational approaches [i.e., Hartree-Fock, Møller-Plesset perturbation theory to the second order, quadratic configuration interaction with single and double excitations, CCSD, CCSD(T), and density functional theory (DFT) with the B3LYP, PBE0, and M06-2X functionals] and basis sets (the aug-cc-pVXZ and aug-cc-pwCVXZ families) for determining the nuclear quadruple coupling constants for AlCN, AlNC, AlSH, AlOH, and AlCCH, where experimental measurements are available. From the results at equilibrium geometries of the polyatomic molecules, it has been determined that (i) the CCSD(T)/aug-cc-pwCVXZ approach is needed to obtain results within 4% of the experimental measurements, (ii) typical DFT values are only within 10%-15% of the experimental measurements, and (iii) the aug-cc-pVXZ family of basis sets is not recommended for computing the electric field gradients at aluminum. The present results also suggest that the NQCC for AlOH should be remeasured. Using the recommended CCSD(T)/aug-cc-pwCVXZ approach, the equilibrium geometries and corresponding NQCCs for AlCH3 and AlCCCN were determined, and the NQCCs are in excellent agreement with previously reported experimental values.
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Affiliation(s)
- Antoine Aerts
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Alex Brown
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
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Okabayashi T, Nakane A, Kubota H, Mitani Y, Yamamoto T, Matsumoto S, Tanimoto M. Fourier transform microwave spectroscopy of AgCN and AuCN. J Mol Struct 2018. [DOI: 10.1016/j.molstruc.2018.03.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Halfen DT, Ziurys LM. The pure rotational spectrum of the T-shaped AlC 2 radical (X[combining tilde] 2A 1). Phys Chem Chem Phys 2018; 20:11047-11052. [PMID: 29610787 DOI: 10.1039/c7cp08613j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The pure rotational spectrum of the AlC2 radical (X[combining tilde]2A1) has been measured using Fourier transform microwave/millimeter-wave (FTMmmW) techniques in the frequency range 21-65 GHz. This study is the first high-resolution spectroscopic investigation of this molecule. AlC2 was created in a supersonic jet from the reaction of aluminum, generated by laser ablation, with a mixture of CH4 or HCCH, diluted in argon, in the presence of a DC discharge. Three transitions (NKa,Kc = 101 → 000, 202 → 101, and 303 → 202) were measured, each consisting of multiple fine/hyperfine components, resulting from the unpaired electron in the species and the aluminum-27 nuclear spin (I = 5/2). The data were analyzed using an asymmetric top Hamiltonian and rotational, fine structure, and hyperfine constants determined. These parameters agree well with those derived from previous theoretical calculations and optical spectra. An r0 structure of AlC2 was determined with r(Al-C) = 1.924 Å, r(C-C) = 1.260 Å, and θ(C-Al-C) = 38.2°. The Al-C bond was found to be significantly shorter than in other small, Al-bearing species. The Fermi contact term established in this work indicates that the unpaired electron in the valence orbital has considerable 3pza1 character, suggesting polarization towards the C2 moiety. A high degree of ionic character in the molecule is also evident from the quadrupole coupling constant. These results are consistent with a T-shaped geometry and an Al+C2- bonding scheme. AlC2 is a possible interstellar molecule that may be present in the circumstellar envelopes of carbon-rich AGB stars.
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Affiliation(s)
- D T Halfen
- Department of Chemistry and Biochemistry, Department of Astronomy, and Steward Observatory, University of Arizona, 1305 E. 4th Street, Tucson, AZ 85719, USA.
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Cabezas C, Barrientos C, Largo A, Guillemin JC, Cernicharo J, Peña I, Alonso JL. Generation and structural characterization of aluminum cyanoacetylide. J Chem Phys 2014; 141:104305. [PMID: 25217914 PMCID: PMC4681119 DOI: 10.1063/1.4894501] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Combined spectroscopy measurements and theoretical calculations bring to light a first investigation of a metallic cyanoacetylide, AlC3N, using laser ablation molecular beam Fourier transform microwave spectroscopy. This molecule was synthesized in a supersonic expansion by the reaction of aluminum vapour with C3N, produced from solid aluminum rods and BrCCCN in a newly constructed ablation-heating nozzle device. A set of accurate rotational and (27)Al and (14)N nuclear quadrupole coupling constants have been determined from the analysis of the rotational spectrum and compared with those predicted in a high-level ab initio study, conducting to the assignment of the observed species to linear AlCCCN. We have searched for this species towards the carbon-rich evolved star IRC + 10216 but only an upper limit to its abundance has been obtained.
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Affiliation(s)
- Carlos Cabezas
- Grupo de Espectroscopia Molecular (GEM), Edificio Quifima, Laboratorios de Espectroscopia y Bioespectroscopia, Unidad Asociada CSIC, Parque Científico Uva, Universidad de Valladolid, Paseo de Belén 5, 47011 Valladolid, Spain
| | - Carmen Barrientos
- Departamento de Química Física y Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid, Campus Miguel Delibes, Paseo de Belén 7, 47011 Valladolid, Spain
| | - Antonio Largo
- Departamento de Química Física y Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid, Campus Miguel Delibes, Paseo de Belén 7, 47011 Valladolid, Spain
| | - Jean-Claude Guillemin
- Institut des Sciences Chimiques de Rennes, École Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, 11 Allée de Beaulieu, CS 50837, 35708 Rennes Cedex 7, France
| | - José Cernicharo
- Group of Molecular Astrophysics, ICMM C/Sor Juana Ines de la Cruz N3 Cantoblanco, 28049 Madrid, Spain
| | - Isabel Peña
- Grupo de Espectroscopia Molecular (GEM), Edificio Quifima, Laboratorios de Espectroscopia y Bioespectroscopia, Unidad Asociada CSIC, Parque Científico Uva, Universidad de Valladolid, Paseo de Belén 5, 47011 Valladolid, Spain
| | - José L. Alonso
- Grupo de Espectroscopia Molecular (GEM), Edificio Quifima, Laboratorios de Espectroscopia y Bioespectroscopia, Unidad Asociada CSIC, Parque Científico Uva, Universidad de Valladolid, Paseo de Belén 5, 47011 Valladolid, Spain
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LI L, SUN M, LI XH, ZHAO ZW, MA HM, GAN HY, LIN ZH, SHI SC, Ziurys LM. Recent Advances on Rotational Spectroscopy and Microwave Spectroscopic Techniques. CHINESE JOURNAL OF ANALYTICAL CHEMISTRY 2014. [DOI: 10.1016/s1872-2040(14)60767-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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