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Abstract The rotational barrier about the CN carbamate bond ofN‐(4‐hydroxybutyl)‐N‐(2,2,2‐trifluoroethyl)tert‐butyl carbamate1was determined by variable temperature (VT)13C and19F NMR spectroscopy. The −CH2CF3 appendage reports on rotational isomerism and allows for the observation of separate signals for the E‐ and Z‐ensembles at low temperature. The activation barrier for E/Z‐isomerization was quantified using Eyring‐Polanyi theory which requires the measurements of the maximum difference in Larmor frequency Δνmax and the convergence temperature Tc. Both Δνmax and Tc were interpolated by analyzing sigmoidal functions fitted to data describing signal separation and the quality of the superposition of the E‐ and Z‐signals, respectively. Methods for generating the quality‐of‐fit parameters for Lorentzian line shape analysis are discussed. Our best experimental value for the rotational barrier ΔGc≠(1)=15.65±0.13 kcal/mol is compared to results of a higher level ab initio study of the modelN‐ethyl‐N‐(2,2,2‐trifluoroethyl) methyl carbamate.
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Measurement of the Ratio between g ‐Factors of the Ground States of 87Rb and 85Rb
Abstract The ratio between the Landég‐factors of the Rb and Rb ground‐state hyperfine levels is experimentally measured to be , consistent with previous measurements. Theg‐factor ratio is determined by comparing the Larmor frequencies of overlapping ensembles of Rb and Rb atoms contained within an evacuated, antirelaxation‐coated vapor cell. The atomic spins are polarized via synchronous optical pumping and the Larmor frequencies are measured by off‐resonant probing using optical rotation of linearly polarized light. The accuracy of this measurement of exceeds that of previous measurements by a factor of ≈50 and is sensitive to effects related to quantum electrodynamics.
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- Award ID(s):
- 1707875
- PAR ID:
- 10078135
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Annalen der Physik
- Volume:
- 531
- Issue:
- 5
- ISSN:
- 0003-3804
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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