Pulse Shape Files

Bruker XWIN-NMR pulse shapes are stored as files in the directory XWINNMRHOME/exp/stan/nmr/lists/wave/. There are three file formats in use: JCAMP-DX, binary and ASCII (text). The binary files can be either RF shapes or Gradient shapes. The shape files included here are either in the JCAMP-DX format (file name extension jc), the binary RF format (file name extension rf) or the ASCII format (file name extension txt).

XWIN-NMR will accept one or two of the file formats for shaped pulses depending on the release. The file format used in the different XWIN-NMR releases are described in the following (taken from the XWIN-NMR release 2.5 online documentation set).

XWIN-NMR 2.0 and later

Pulse shapes are stored in the directory XWINNMRHOME/exp/stan/nmr/lists/wave/ in ASCII format conforming to JCAMP-DX. The data points represent the amplitude and phase values.

XWIN-NMR versions earlier than 2.0

Pulse shapes are stored in the directory XWINNMRHOME/exp/stan/nmr/lists/wave/. There are two types of data formats, a binary one required by XWIN-NMR for the execution of shaped pulses, generated by the program shape, and a text format which can be read into shapee by the command ar, and stored back in binary format by w for use with XWIN-NMR.

Text Format

The text format is particularly useful if you want to generate own shapes by a suitable program. The file starts with the text RFVERSION_F, then the pulse shape follows. The first column contains the amplitudes, the second one the corresponding phases. If the phases are omitted, the following rule applies: the phases are set to 0 if the amplitudes are positive, and to 180 degrees if negative. Phases are specified in degrees in the range 0-360 (floating point numbers are legal). A file must not contain more than 32768 lines. Amplitudes and phases are separated by a space, tabulator, or comma.

Relative power values may range from 0-100. If a value in the file exceeds 100, it will be rescaled to 100 during execution. All other points will be rescaled accordingly. Values less than 100 will not be rescaled.

Binary Format

The binary file format of shape files is as follows:

• Header: consists of 256 32 bit float words.
  1. word 1 contains file type information: 371242.0 (= GRADVERSION_F) or 18906.0 (= RFVERSION_F)
  2. word 2 contains # of amplitudes (=amps) stored
  3. word 3 contains # of phases (=phas) stored
  4. word 4 to word 256 are unused
• Data: consists of (amps + phas) 32 bit float words.
  1. RFVERSION: pairs of phases and ampitudes: phases (in degrees) from 0.0 to 360.0 and amplitudes from 0.0 to 100.0 %. Phases are always stored as first value followed by the corresponding amplitude.
  2. GRADVERSION: only amplitudes are stored (values from 0.0 up to 100.0 %). Phases allowed are 0.0 and 180.0 degrees. If the phase is 180.0 degrees, the stored amplitude is negated. No phases are stored in the file.

The maximum size of amplitudes (for GRADVERSION) or pairs of amplitudes and phases (=RFVERSION) is 32K (or 32768 points/pairs).