Mononitrosyl complexes of general composition [ML5NO]n± (M=transition metal, L=ligand such as F,Cl,Br, CN, etc) can form linkage isomers upon irradiation with light in the visible spectral range. We aim to measure the structure of the MS2 state, corresponding to a nitrosyl linkage isomer, in sodium nitroprusside (Na2[Fe(CN)5NO]2H2O ) after pulsed laser excitation. Based on ultrafast UV/Vis and infrared spectroscopy, the MS2 state is expected to be occupied within 10 ps. Thus a diffraction experiment with a time resolution of 10-100 ps at room temperature (at room temperature MS2 has a lifetime of 300ns) would prove that SNP has indeed equilibrated in the MS2 minimum after only 10 ps. This experiment would also demonstrate the possibility to capture full structures on single crystals at such a short time scale.