pulsfolgen

Pulsfolgen, or pulse sequences in English, are sequences of energy pulses used to excite, probe, and measure a system’s time-dependent response. They can be periodic or aperiodic and are defined by properties such as pulse duration, amplitude, shape, and the timing between pulses (the repetition interval). Pulsfolgen are employed across several disciplines, including magnetic resonance, ultrasonography, optics, radar, and electronics, to extract information about structure, dynamics, or material properties.

In magnetic resonance (NMR and MRI), a pulse sequence consists of radiofrequency pulses combined with gradient fields. The sequence manipulates spin states and encodes spatial or chemical information, with key parameters like flip angle, pulse duration, repetition time (TR), and echo time (TE). Common families include spin-echo, gradient-echo, inversion-recovery, and echo-planar imaging. In NMR spectroscopy, pulse sequences enable multidimensional experiments (for example, COSY or HSQC) that reveal interactions between nuclei.

Beyond magnetic resonance, pulsed emissions are central to ultrasound, optics, radar, and lidar. Short pulses of sound or light allow time-of-flight measurements, depth profiling, Doppler sensing, or high-peak-power excitation. Pulse shaping and precise timing improve resolution, contrast, and signal-to-noise, while duty cycle and spectral content influence heating and energy efficiency. Design considerations also address artifacts from mis-timing, phase errors, or imperfect pulse shapes.

Interpreting data from pulsfolgen often involves modeling the system response as a function of the pulse sequence, using concepts such as convolution, coherence pathways, and impulse responses. Advances in pulse sequence design continue to enhance temporal resolution, sensitivity, and the ability to probe fast or subtle dynamics in complex systems.