s, and a recycle time of 0.9 s was used. The spectral widths selected were 16129 Hz (160 ppm) for carbon and ±1410 Hz for proton, with an initial data matrix size of 256 W X 4K (í" t2). The data were processed in the usual fashion. The experiment was performed on approximately 50 mg of pulvomycin, dissolved in 0.5 mL of CD3OD, and accumulation of data required approximately 14 h.
The high-temperature AIF' radical cation has been generated by the photoionization of AlF(g) produced both by a laser sputtering method and high-temperature vaporization reactions. This represents the first spectroscopic study of AIF' and establishes its ground electronic state as 22. The ESR spectrum of the AIF+ radical, isolated in a neon matrix at 4 K, has been analyzed in detail, and the experimental magnetic parameters obtained show excellent agreement with the results of an extensive ab initio theoretical calculation. The AIF' magnetic parameters in a neon matrix are the following: g,, = 2.0015 (S) , g, = 2.0000 (5); AI, All = 2893 (8) MHz, A , = 2782 (6) MHz, I9F, A,, = 473 (5) MHz, A , = 90 (5) MHz. The electronic structure of AIF' is compared to the isoelectronic series 29SiO+, AIO, and MgF utilizing both experimental and theoretical findings. Orbital populations for the unpaired electron were obtained from the commonly applied free atom comparison method (FACM) and from a Mulliken type population analysis of a CI wave function which yielded magnetic parameters in close agreement with experiment. The effect of 'corwther valence overlap" was studied in detail for this isoelectronic series. This A l p study and a previous one for SiO+ are apparently the first ESR investigations of high-temperature inorganic cation radicals. Generation and trapping techniques have been developed to permit the ESR (electron spin resonance) investigation of small, highly reactive cations having relatively large electron affinities in neon matrices near 4 K. Examples of cations recently studied by ESR with these neon matrix trapping techniques include CO+,I NH3+,' N2+,2 H20+,3 H2CO+,4 Cd+,s CH4+: C202+,' and the high-temperature cation radical 2gSiO+.8 Experimental results have also been obtained for a few anion radicals trapped in neon matrices as free ions including F2-,9 H F , I 0 DF,Io CI,-,'O and HCI-.'O The Cl; and HCI-radicals have been previously studied by ESR as chemically bonded ion pairs, M'X-, in argon ma-The inert nature of the neon host, its low polarizability, and large ionization energy (21.6 eV) allow free or gas-like properties of ions to be obtained. Cations having electron affinities much greater than 10-1 1 eV apparently cannot be stabilized in other matrix materials such as argon or freon matrices. Paramagnetic ions trapped in frozen ionic solutions or crystalline hosts can be highly perturbed, and the information obtained might not accurately represent the inherent properties of the trapped species. This AIF' study illustrates that the matrix isolation trapping method could be applied to a wide range of charged and neutral chemical systems produced by reactive laser sputtering processes. The reactive intermediates produced by such laser induced gassurface reactions could be characterized by the wide range of spectroscopic methods currently used with the matrix isolation technique. Current research efforts in our laboratory are using this laser technique to produce metal nitride neutral and cation radica...
The anion radical F−2 has been generated and trapped as a free ion in dilute neon matrices near 4 K and investigated by electron spin resonance (ESR). The magnetic parameters obtained in neon are: g∥ =2.0018(3); g⊥ =2.0185(3); A∥ =913.5(4), and A⊥ =−22.5(4) G. The neon ESR measurements are the first gas-like results and these are compared with earlier findings for F−2 in various crystalline environments. Analysis of the combined results reveal that F−2 is the most gas-like or least perturbed in the larger ionic lattices. The information obtained should be useful in estimating the degree of perturbation that typically exists for the many radicals which have been studied in ionic crystalline environments. Based upon these experimental findings for F−2 in neon matrices, an atomic value of Adip for a fluorine atom is proposed for estimating P orbital spin densities in ionic fluorine compounds. This experimental Adip for 19F is compared to commonly used theoretical values.
The 11BF+ and 10BF+ radical cations have been generated and trapped in neon matrices at 4 K using the combined techniques of pulsed reactive laser sputtering and photoionization at 16.8 eV. An independent high temperature source of BF(g) in conjunction with photoionization was also employed and a comparison between these two different generation methods reveals no significant differences in their ESR spectra. The magnetic parameters for 11BF+ measured in neon matrices are g∥=2.0012(3), g⊥=2.0004(3), (11B) A∥=1784(1), and A⊥=1727(1) MHz, (19F)A∥=410(1), and A⊥=152(1) MHz. Extensive ab initio theoretical calculations have been conducted for BF+ and the nuclear hyperfine properties obtained from various types of CI wave functions show excellent agreement with the experimental measurements. Valence orbital occupancies obtained from a Mulliken-type population analysis performed on the CI wave functions are compared with the conventional free atom comparison method for obtaining electronic structure information from ESR A tensor measurements. The distribution of the unpaired electron in BF+ is compared to six other isoelectronic first row radicals.
The AlF+ radical cation has been studied spectroscopically for the first time and found to have a 2E ground state.
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