Begleitzuständen

Begleitzustände (accompanying states) is a term used in German-language physics and chemistry to describe secondary quantum states that occur together with a primary state during a process. They arise from couplings to other degrees of freedom or to additional particles and can influence observable properties without being the main state of interest.

In spectroscopy and molecular physics, Begleitzustände often appear as vibronic or vibro-rotationally coupled states that accompany an electronic transition. They can produce satellite lines, sidebands, or broadened features in spectra and affect transition intensities through coupling constants and Franck–Condon factors. In dynamics and decay processes, accompanying states can participate in cascades or resonant pathways, modifying decay rates and branching ratios.

In solid-state and condensed-matter systems, Begleitzustände may involve excitations that accompany a primary quasiparticle, such as phonon-assisted or exciton-phonon complex states, which influence optical responses and transport properties. The concept is usually descriptive, emphasizing the role of coupling, correlation, or multi-degree-of-freedom dynamics rather than serving as a rigid technical category.

Terminology and usage vary by field and author. Begleitzustände are often discussed alongside related ideas such as satellite states, sidebands, or coupled states, with the precise meaning depending on the physical system under consideration. The term highlights how auxiliary states accompany a principal state and modify observable phenomena through interactions within the system.