ROTATIONALLY RESOLVED MAGNETIC VIBRATIONAL CIRCULAR-DICHROISM - EXPERIMENTAL SPECTRA AND THEORETICAL SIMULATION FOR DIAMAGNETIC MOLECULES

The rotationally resolved magnetic vibrational circular dichroism (RR MVCD) spectra of the diamagnetic molecules DCl and NH3 are analysed on the basis of theoretical simulation. Basic theoretical equations are derived for the RR MVCD dispersed intensity pattern from the conventio nal rovibrational energy level expression. This provides a convenient method for interpretation of MVCD spectra in terms of fundamental spec troscopic parameters. Good agreement was obtained between the simulate d and the experimental data measured for DCl and NH3. Minor deviations from the theory occur in the dipole strength distribution for DCl, bu t this is corrected by measuring the A(1)/D-0 ratio, from which the mo lecular g value can be determined for resolved transitions. Although m agnetic properties of DCl and NH3 are known, this study demonstrates t he ability of MVCD to provide an alternate method of determining molec ular g-values as compared to classical microwave studies of the Zeeman effect. The data further show that experimentally observed RR MVCD sp ectra are fully explained using the conventional theory for rovibratio nal transitions under Zeeman perturbation. Variations of magnetic para meters of the ground and excited vibrational states of these molecules cause characteristic changes of the MVCD band intensity patterns. The se variations are used to evaluate approximations made in previous mom ent analyses of RR MVCD spectra and to delimit the sensitivity of the RR MVCD technique to differences in ground and excited state g-values.