Spin-rotation constants for

Recent reports of spin-rotation constants for aluminum chloride (35) and aluminum isocyanide (36) have made possible the comparison of experimental and ab initio calculated shielding results. If one were able to measure the27A1 chemical shift of one or both these compounds, it would be possible, in principle, to establish an absolute shielding scale for aluminum however, the high reactivity of these compounds has so farprecludedsuchmeasurements. High-resolution microwave measurements have also been recently carried out on A1H (37) however, analysis of the data did not consider the 27A1 spin-rotation interaction (vide infra). 

Kobayashi, Goto, Yamamoto and Saito [154] were able to determine five of the six molecular parameters listed above, only the nuclear spin rotation constant for the 14N nucleus being too small to be significant. The molecular parameters and conclusions about the spin density distribution for both the a 1A and X 3XG states are fisted in table 10.14. 

Absolute Shielding Scales. - Gee and Wasylishen have recommended that the microwave study of AlH be repeated, as the previous one failed to account for the Al nuclear spin-rotation interaction. Their ab initio calculations give a range of values depending on the method used but are all of the order of 300 kHz. The value of the spin-rotation constant for Al in AIF, on the other hand, has been measured, Cj = 8.2 1.3 kHz, which leads to (ct — CTj ) = 320 50 ppm for Al in AIF and... 

A microwave study of the spin-rotation tensor of GaF in the gas phase has been reported by Wasylishen et al This provides spin-rotation constants for both the F and the Ga nucleus. A value of (an — aj ) = 945 35 ppm for Ga is derived from the experimental spin-rotation constant. The absolute Ga isotropic shielding obtained from the experimental spin-rotation constant at the ground vibrational state of GaF is... 

The paramagnetic term aP = -386.56 0.63 ppm was obtained after improving the spin-rotation constants [3] using more accurate rotational constants of PH3 [13, 14]. The ab initio calculated diamagnetic contribution =981.01 ppm was taken from [15]. - The spin-rotation constants for PH3 in the vibrational ground-state [3] were recalculated in line with the PH3 equilibrium geometry. [15] was used as above. - op=-366.43 ppm was derived from the measured spin-rotation constants. The calculation of according [16] yielded 960.83 ppm [3]. 

The rotational and spin-rotation constants for the ground state X Bi, v = 0 were obtained from analyses of the microwave (MW) spectrum [1 ] and of the highly resolved absorption lines (IR laser spectroscopy) of the vi fundamental band [2]. Constants for the vibrationally excited states Vi=1 [2] and Va=1 [3] were obtained from the IR laser spectra of the and V3... 

Hindermann, D. K. and Cornwell, C. D. (1968). Vibrational corrections to the nuclear-magnetic shielding and spin-rotation constants for hydrogen fluoride shielding scale for F. J. Chem. Phys., 48, 4148-4154. 

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