Devon W. Hill

Electron spin resonance investigation of Sc+2 in neon matrices and assignment of its ground electronic state as X 4Σ−. Comparison with theoretical calculations

The discandium radical cation, Sc+2, has been isolated in neon matrices at 4 K and studied by electron spin resonance (ESR) spectroscopy and theoretical methods. It was produced by the x‐irradiation of neon matrix samples containing neutral Sc2 which was formed by trapping the products generated from the pulsed laser vaporization of scandium metal. The experimental and theoretical findings indicate that Sc+2 has a 4Σ−g electronic ground state compared to an X 5Σ−u state for the neutral discandium radical. The large decrease in the 45Sc hyperfine interaction (A tensor) going from Sc2 to Sc+2 provides direct experimental information concerning the types of valence molecular orbitals that are involved in these diatomic radicals. The neon matrix magnetic parameters for 45Sc+2 are g∥≊2.00, g⊥=1.960(1), ‖A∥‖=28(6), and ‖A⊥‖=26.1(3) MHz; the D value (zero field splitting) was 15 381(3) MHz. Ab initio configuration interaction (CI) calculations of the nuclear hyperfine interactions yielded results in reasonable a...

Electron‐spin‐resonance studies of 12CH3F+, 13CH3F+, and 12CH2DF+ in neon matrices at 4 K: Comparison with theoretical calculations

Various isotopic forms of the methyl fluoride cation 12CH3F+, 13CH3F+, and 12CH2DF+ have been generated by photoionization at 16.8 eV and separately by electron bombardment at 50 eV. The first electron‐spin‐resonance (ESR) results are reported for this radical cation which was isolated in neon matrices at 4 K. The measured A tensors or nuclear hyperfine parameters were compared with the results obtained from various computational approaches. Surprising observations were the large amounts of spin density on the methyl group, especially the hydrogen atoms, and the extreme differences in the deuterated spectra compared to the nondeuterated case. The presence of a single D atom apparently acts to prevent dynamic Jahn–Teller averaging which makes the methyl hydrogens equivalent on the ESR time scale. Such a dramatic Jahn–Teller effect has been previously observed for the similar methane cations CH+4 and CH2D+2. The magnetic parameters for CH2DF+ in neon at 4 K are gX=2.0032(5), gY=2.0106(8), and gZ=2.0120(5); ...

Laser vaporization generation of the diatomic radicals PdB, 105PdB, PdAl, and 105PdAl: Electron spin resonance investigation in neon matrices at 4 K

The new diatomic radicals PdB and PdAl have been generated by depositing the products produced from the pulsed laser vaporization of the elemental mixtures into neon matrices at 4 K. ESR (electron spin resonance) studies of these matrix isolated radicals, including an analysis of the 105Pd(I=5/2), 27Al(I=5/2), and 11B(I=3/2) nuclear hyperfine interactions, show that both have X 2Σ electronic ground states. These new results are compared with previous ESR measurements for PdH, PdCH3, YPd, ScPd, and PdH2+ to reveal electronic structure information and bonding trends as the complexity of the ligand increases 1s, 2p, 3p, 3d, and 4d. Ab initio UHF (unrestricted Hartree–Fock) theoretical calculations were also conducted on four of these small palladium radicals as part of this experimental investigation. A simple interpretation of the 105Pd hyperfine interactions and molecular g tensors based on the degree of charge transfer to palladium is presented. The observed magnetic parameters (MHz) for 105Pd11B in a neo...

Electron spin resonance rare gas matrix studies of 12CO2−, 13CO2−, and C17O−2: Comparison with ab initio calculations

The 12C16O2−, 13C16O2−, 12C17O2−, and 12C16,17O2− radical anions have been generated by four independent methods and isolated in neon and argon matrices for detailed ESR (electron spin resonance) investigations. Included with these experimental measurements for the various magnetic parameters of CO−2 are high level ab initio calculations (MR SD‐CI and others) of the 13C and 17O hyperfine A tensors. Some of the calculations included the effects of a 42‐atom neon cage on the electronic structure of CO−2. Previous ESR studies of CO−2 have been conducted in more perturbing environments, such as ionic crystals, where the close proximity of the counter cation can alter the anion’s properties. A comparison of the earlier measurements in more interactive materials with these theoretical and rare gas matrix results reveals a significantly different distribution of the spin density. The neon magnetic parameters (MHz) for CO−2 are gx=2.0018, gy=1.9964, gz=2.0010; for 13C, Ax=320.4, Ay=296.1, Az=394.5; for 17O, Ax=−8...