DeerAnalysis2006 - a comprehensive software package for analyzing pulsed ELDOR data

Pulsed electron-electron double resonance techniques such as the four-pulse double electron-electron resonance experiment measure a dipolar evolution function of the sample. For a sample consisting of spin-carrying nanoobjects, this function is the product of a form factor, corresponding to the internal structure of the nanoobject, and a background factor, corresponding to the distribution of nanoobjects in space. The form factor contains information on the spin-to-spin distance distribution within the nanoobject and on the average number of spins per nanoobject, while the background factor depends on constraints, such as a confinement of the nanoobjects to a two-dimensional layer. Separation of the dipolar evolution function into these two contributions and extraction of the spin-to-spin distance distribution require numerically stable mathematical algorithms that can handle data for different classes of samples, e.g., spin-labelled biomacromolecules and synthetic materials. Furthermore, experimental imperfections such as the limited excitation bandwidth of microwave pulses need to be considered. The software package DeerAnalysis2006 provides access to a comprehensive set of tools for such data analysis within a common user interface. This interface allows for several tests of the reliability and precision of the extracted information. User-supplied models for the spin-to-spin distance distribution within a certain class of nanoobjects can be added to an existing library and be fitted with a universal algorithm.