Thursday, August 14, 2008
Pulse Sequences to Minimize Acoustic Ringing
Acoustic ringing can be a real problem at low frequencies. Its effects can be minimized in a simple one-pulse spectrum by either throwing away the initial bad data and applying a large phase correction or by using backward linear prediction to calculate the lost data. There are a number of pulse techniques one can use when collecting the data to cancel out the ringing. Two such examples are shown in the figure below. The bottom spectrum is the result of a simple one pulse experiment. The middle spectrum was collected using Bruker's "aring" pulse program and the top spectrum was acquired using Bruker's "aring2" pulse program. In all three cases a simple Fourier transform was applied with exponential line broadening. The spectra were collected with the same number of scans on a 300 MHz instrument.