NMR500 Basic Operation

Basic Steps


When NOT to spin

For best lock stability:


Channels and Nuclei

An indirect detection probe (IDP) is designed for optimal H1 direct detection and indirect detection (through transient 2nd or 3rd dimension) of other nuclei. A broadband probe (such as the switchable probe or SWP on NMR500) is optimized for broadband nucleus direct detection while decoupling H1 or F19. A broadband nucleus is any nucleus other than H1 and F19 carrying lower Larmor frequency.

Each probe is designed with a fixed number of channel inputs for nuclei in different frequency range. On a broadband probe, such as SWP, there are typically three channel inputs: 1H, X nucleus, and the lock (2H). The X channel can be set to any broadband nucleus with a change of a tuning stick (no stick is needed for C13).

The name "channel" is a confusing name that is still being widely used. Do not confuse the “channel” (input ports) on the probe with the channel names in the console and the channels in vnmrJ. The three "channel" names are completely separate in principle. In the console, a channel refers to an amplifier output. In vnmrJ, the channel name is a more abstract, but each channel is usually tied with an amplifier output in the console and carrying a frequency bandwidth. The channel mapping and signal routing are mostly automatic, but can also be manipulated by users. On NMR500, channels 1 and 2 in the console are full-band (covering both high 1H/19F and low frequencies for X nuclei), equivalent and can be set to any nucleus. In most experiments on NMR400 and 500, only channel 1 and sometimes channels 1 and 2 are used. Channel 1 in vnmrJ is usually also the direct detection channel.

Direct Detection and Decoupling

In vnmrJ, channel 1 is used for direct detection. Channels 2, 3 ... are called decouplers (decoupler 1, decoupler 2 ...) for historical reasons. For example, C13 direct detection involves setting channel 1 to C13 and channel 2 to H1 (decoupling). Each channel has its own default parameter names for hardware and data collection parameters. The most important parameters you may encounter are:

Probe Tuning

NOTE: New arrangement requires all users not to tune the probe unless permitted by the Manager. The instrument should be left tuned for H1 and C13 detection with a default CDCL3 solvent.

Brief Tuning Steps

SWP Tuning

NOTE: Before tuning, make sure to have the right nucleus setting for the channel used (type tn? for channel 1, dn? for channel 2 to check.). Type su before tuning.

**For 1H or 19F tuning

For F19, make sure to replace the filter on the right side of preamp to a F19 filter.

**For broadband nucleus (C13, P31, Li7, N15 ... etc) tuning.

Detailed Tuning Steps for H1 and F19

This instruction is for the SWP probe on NMR500, but it generally applies to other probes on NMR500 with minor changes.

First, load the experiment to be performed and make sure the channels to be tuned have the right nucleus setting. To find out this info, type tn? (for channel 1), or dn? (for channel 2). If it is not the intended nucleus, for tuning purpose you can simply enter at the command line under any experiment, for example, tn='C13' or dn='H1' and then tune channel 1 for 13C and channel 2 for H1. Type su before tuning.

**For H1 Tuning

No tuning stick is needed for 1H tuning.

**For F19 tuning

Detailed Steps to Tune for X-nucleus (C13, P31, .. etc)

The procedure is similar to H1 channel tuning. Read H1 tuning procedure above for additional details. The tuning procedure for any broadband nucleus is identical, except:


H. Zhou updated Aug 2011