**Software for the calculation of paramagnetic enhancements of nuclear relaxation rates in slowly rotating systems**

**Reference:**

Bertini I, Galas O, Luchinat C, Parigi G, 1995, *J Magn Reson Ser A* 113:151.

The NMRD program is available here: NMRD Fortran source code

For a README file click here: README

An example of an input file: PARC.DAT

**Presence of Static ZFS**A theoretical treatment for the field-dependence of electron spin relaxation in the presence of static ZFS under slow rotation conditions has been incorporated in the NMRD program for nuclear spin relaxation in paramagnetic systems

**References:**

Bertini I, Kowalewski J, Luchinat C, Nilsson T, Parigi G, 1999, *J Chem Phys* 111:5795-5807.

Kruk D, Nilsson T, Kowalewski J, 2001, *Phys Chem* 3:4907-4917.

The Fortran source code is available here: Fortran source code

An example of an input file: PARC.DAT

**Inclusion of the Calculation of Proton Relaxation of Superparamagnetic Particles in the NMRD program**

The calculation of the superparamagnetic outer-sphere relaxation as developed by the Mons-Hainaut group (Roch A, Muller RN, Gillis P, 1999, *J Chem Phys* 110:5403) is now included inside the Florence NMRD program, which makes the program more complete. The calculations can be performed with consideration of the complete theoretical calculations or a heuristic equation which reproduces the gradual transition from the region with dominant anisotropic energy to dominant Zeeman energy. In the input file, some additional parameters must be provided, according to the theory for the superparamagnetic relaxation, namely the N?el relaxation time, which describes the coherent electron spin transitions within the superparamagnetic crystal, the diffusion coefficient, the size of the crystal, the magnetization at saturation (which allows us to take into account the magnitude of the "superspin", i.e. the unique magnetic moment of the SPM particle), and the anisotropy energy (given by a material constant times the volume of the crystal). The heuristic equation contains three additional adjustable parameters, depending on the ratio anisotropy energy/thermal energy.

The Fortran source code is available here: SuperNMRD Fortran source code

An example of an input file: PARC.DAT