Collision spectroscopy in isomer characterization: The case of (E)‐ and (Z)‐p‐nitrophenyldiazo tert‐butyl sulphides

The structural characterization of the E and Z isomers of p‐nitrophenyl‐diazo tert‐butyl sulphide has been achieved by means of different ionization methods (electron impact, fast atom bombardment, positive‐ion chemical ionization) and collision experiments performed under different kinetic energy regimes (high‐ and low‐energy collisions, angle‐resolved mass spectrometry and energy‐resolved mass spectrometry). The two compounds give rise to identical fragmentation patterns. Collision experiments, both at low energy and in the keV range at a scattering angle of 0°, in M^+· species obtained by electron impact on the two isomers, do not show any significant differences; the same experiments performed with 8 keV ions at a scattering angle of 2° indicate a clear difference in the absolute abundances of the two main daughter ions. High‐energy collisions of MH⁺ ions obtained by fast atom bombardment lead to different spectra at both 0° and 2° scattering angles, proving that the energy deposition in the preselected species is an important parameter. Low‐energy collisions with argon of MH⁺ ions generated by positive‐ion chemical ionization (NH₄ ⁺) give rise to almost identical energy‐resolved mass spectra, whereas the same experiments using helium as target gas lead to a clear distinction between the two isomers.