Angular distributions of fragment ions arising from tetrahedral CH3I and isomer identification using intense laser fields

Utilizing an ultraintense (10(16) W cm(-2)) Is laser, the laser/matter inte raction of the tetrahedral CH3I molecule is investigated. A mass spectrum a nd the angular distributions of fragment ions arising from Coulomb explosio n of molecular ions, obtained with linearly polarized light, are presented. The distributions for In+ (n less than or equal to 7), CHm+ (m less than o r equal to 3), Cp+ (p less than or equal to 4) and H+ ions are all anisotro pic and maximal when the polarization lies along the spectrometer axis. The molecule hence seems to behave as a diatomic, with the fragment ions being ejected along the field direction. Also presented are mass spectra of the isomers 1- and 2-nitropropane, which are explosive species, taken for horiz ontal and vertical polarizations at both 375 and 750 nm. It is shown that f emtosecond laser mass spectrometry (FLMS) can be used to distinguish betwee n these two isomers through their differing dissociation patterns. Isomer i dentification is important for many different applications and FLMS may pro vide a means of achieving this for a wide range of molecules.