Locking in vnmr

From NMR Wiki

Figure 1. Default view of vnmr Acqi window. Buttons "Insert/Inject" control position of sample. Button "Close" will close the window. Other buttons will allow access to different controls of interactive acquisition.

Figure 2. Lock controls. Buttons "On" and "Off" turn field frequency lock on and off. Data panel with black background shows FID of lock nucleus.

Figure 3. Lock nucleus FID.

In the vnmr command line type 'acqi' or click 'Acqi' button. A window as shown on Fig. 1 will open. Now click "Lock" button. The window will change into something like you can see on Fig. 2 or 3.

The curve that you see in the window with black background is an FID (free induction decay) of lock nucleus (most often-deuterium). Ideally frequency of the lock channel transmitter should be set exactly at larmor frequency of that nucleus. If that condition is met

Lock level is weak in Fig. 2., while in Fig. 2 lock