Molecular Beam Electric Resonance Spectroscopy

Zorn, Jens C.; English, Thomas C.

doi:10.1016/s0065-2199(08)60117-7

Cited by 25 publications

(10 citation statements)

References 251 publications

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“…Complete J tensors can be characterized by studying the NMR spectra of single crystals, solid powder samples, , or samples oriented in liquid crystalline solvents . Another less well-recognized source of spin−spin coupling tensor information is the hyperfine structure observed in molecular beam or high-resolution microwave spectroscopy experiments. The importance of experimental data from the latter experiments, with few exceptions, has been completely overlooked.…”

Section: Introduction and Contextmentioning

confidence: 99%

“…The theory of indirect spin−spin coupling was originally described by Ramsey. ,19a,b, Qualitatively, the indirect nuclear spin−spin coupling may be pictured as a two-step process, in which one nucleus polarizes neighboring electrons, and this polarization is transferred via the electronic network to a second nucleus. There are three basic mechanisms by which the nucleus may interact with neighboring electrons.…”

Section: Introduction and Contextmentioning

confidence: 99%

“…In the absence of any external fields, the hyperfine Hamiltonian for 35 Cl− 19 F may be expressed as follows: which describe the 35 Cl quadrupolar, 35 Cl spin-rotation, 19 F spin-rotation, tensor spin−spin, and scalar spin−spin interactions, respectively. It is well-known that the nuclear spin-rotation constants c Cl and c F are related to the nuclear magnetic shielding tensors, 19b, and it is understood in the literature that c 4 corresponds to J iso . What is not generally recognized is the significance of c 3 , in particular the indirect spin − spin coupling contribution to c 3 .…”

Section: Introduction and Contextmentioning

confidence: 99%

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Indirect Nuclear Spin−Spin Coupling Tensors in Diatomic Molecules: A Comparison of Results Obtained by Experiment and First Principles Calculations

Bryce

Wasylishen

2000

J. Am. Chem. Soc.

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The importance of hyperfine structure observed in molecular beam or high-resolution microwave spectroscopy experiments has been almost completely overlooked by NMR spectroscopists and theoreticians. In the present work, we show for a series of diatomic molecules that the indirect spin-spin coupling tensor, of fundamental importance to magnetic resonance spectroscopy, is completely characterized by the hyperfine measurements. The hyperfine parameter c 4 is known to be equivalent to the isotropic spin-spin coupling constant, J iso ; what has not been exploited is the relationship between c 3 and the anisotropic portion of the spin-spin coupling tensor, ∆J. Through comparisons to highly precise experimental data available for LiH, LiF, KF, Na 2 , and ClF, multiconfigurational SCF calculations using balanced complete active spaces and large correlation-consistent basis sets have been employed to establish the reliability of such calculations for determining the complete tensor rather than simply J iso . The experimental data are for "isolated" molecules, making them ideal for comparison with ab initio results; agreement is generally within a few percent after accounting for rovibrational effects. These results, combined with further calculations on a larger set of diatomic molecules (HF, BF, AlF, KNa, HCl, NaF), provide new insights into the nature of indirect spin-spin coupling. Calculations indicate the importance of each of the various coupling mechanisms. The influence of the Fermicontact mechanism, traditionally thought to be the dominant contribution to J iso , is shown to vary considerably even for couplings between first-row elements. General conclusions about the relative importance of all mechanisms to both the isotropic and anisotropic portions of the coupling tensor are discussed, and periodic trends are proposed.

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Section: Introduction and Contextmentioning

confidence: 99%

Section: Introduction and Contextmentioning

confidence: 99%

Section: Introduction and Contextmentioning

confidence: 99%

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Indirect Nuclear Spin−Spin Coupling Tensors in Diatomic Molecules: A Comparison of Results Obtained by Experiment and First Principles Calculations

Bryce

Wasylishen

2000

J. Am. Chem. Soc.

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“…These expressions correspond to the NMR-based equations described above such that c 4 = J iso and c 3 = R eff . These relationships have been alluded to; ,, however , they are not widely appreciated in the NMR community.…”

Section: Overview Of Nuclear Spin Interactions: the Connectionsmentioning

confidence: 99%

“…The purpose of this Account is to present the important, but widely overlooked, connections between these two seemingly disparate areas of spectroscopy, in the context of our recent experimental and computational investigations of their relationship. Specifically, we will discuss the information that one can extract from the hyperfine structure (hfs) present in high-resolution microwave experiments and molecular beam experiments [7][8][9][10][11] and contrast this information with the "observables" from NMR experiments. Due to the complicated nature of the interactions involved, the discussion will focus on small molecules, particularly on diatomic molecules.…”

Section: Introductionmentioning

confidence: 99%

Microwave Spectroscopy and Nuclear Magnetic Resonance SpectroscopyWhat Is the Connection?

Bryce

Wasylishen

2003

Acc. Chem. Res.

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The history and development of microwave spectroscopy and nuclear magnetic resonance (NMR) spectroscopy have much in common. In this Account, we discuss the less widely appreciated connections between the parameters measured using the two techniques. Selected examples from our laboratory and from the recent literature attest to the utility and importance of these connections. For example, how are nuclear spin-rotation tensors and NMR chemical shifts related? Why should chemists be interested in absolute magnetic shielding scales? What can chemists learn about trends in spin-spin coupling constants from the hyperfine parameters measured in microwave and molecular beam experiments? The increasingly important role of quantum-chemical calculations in the interpretation of the microwave and NMR data is also highlighted.

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Bibliography

2005

Molecular Physics

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Molecular Beam Electric Resonance Spectroscopy

Cited by 25 publications

References 251 publications

Indirect Nuclear Spin−Spin Coupling Tensors in Diatomic Molecules: A Comparison of Results Obtained by Experiment and First Principles Calculations

Indirect Nuclear Spin−Spin Coupling Tensors in Diatomic Molecules: A Comparison of Results Obtained by Experiment and First Principles Calculations

Microwave Spectroscopy and Nuclear Magnetic Resonance SpectroscopyWhat Is the Connection?

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