Double-Quantum Axes

Some 13C-13C correlation spectra can be recorded with a double quantum chemical shift axis in the indirect dimension (e.g. INADEQUATE, POST-C7 etc.). The observed chemical shift is then the sum of two individual chemical shifts and pairs of peaks are observed at positions δ1,(δ1+δ2) and δ2,(δ1+δ2). When reading in such a spectrum you should select the C[CC(DQ)] Experiment Type. A modified diagonal is now drawn at along (δ, 2δ). The mouse will have crosshairs at both δ1 and δ2 in the direct dimension and at (δ1+δ2) in the indirect dimension. Mouse crosshairs will also be replicated at the two single quantum chemical shifts in all the other windows for easy comparison with other spectra (it may be necessary to make sure that the Panel Type in the Window, Edit Windows popup for the single quantum dimension is the same as that for your other single quantum windows).

When making assignments for such a DQ spectrum, the chemical shift sum in the indirect dimension is automatically split into its two constituent single quantum chemical shifts. Assignment options for these are presented and be selected as normal.