TY  - JOUR
AU  - Stanek, Daniel
AU  - Fauseweh, Benedikt
AU  - Stihl, Christopher
AU  - Pasini, Stefano
AU  - Uhrig, Götz S.
TI  - Anomalous behavior of control pulses in presence of noise with singular autocorrelation
JO  - Journal of magnetic resonance
VL  - 245
SN  - 1090-7807
CY  - Amsterdam [u.a.]
PB  - Elsevier
M1  - FZJ-2015-01138
SP  - 133 - 142
PY  - 2014
AB  - We report on the anomalous behavior of control pulses for spins under spin–spin relaxation and subject to classical noise with a singular autocorrelation function. This behavior is not detected for noise with analytic autocorrelation functions. The effect is manifest in the different scaling behavior of the deviation of a real pulse to the ideal, instantaneous one. While a standard pulse displays scaling View the MathML source∝τp1, a first-order refocusing pulse normally shows scaling View the MathML source∝τp2. But in presence of cusps in the noise autocorrelation the scaling View the MathML source∝τp3/2 occurs. Cusps in the autocorrelation are characteristic for fast fluctuations in the noise with a spectral density of Lorentzian shape. We prove that the anomalous exponent cannot be avoided; it represents a fundamental limit. On the one hand, this redefines the strategies one has to adopt to design refocusing pulses. On the other hand, the anomalous exponent, if found in experiment, provides important information on the noise properties.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000340690300018
C6  - pmid:25036295
DO  - DOI:10.1016/j.jmr.2014.06.009
UR  - https://juser.fz-juelich.de/record/187509
ER  -