Photodissociation mass spectra and mass-selected resonant (1+1)-photodissociation spectroscopy of some alkyl iodide radical cations

摘要

Photodissociation mass spectra and mass selected (1+1)-photodissociation spectra of C_2H_5I ~(+?), C 2D_5I~(+?), 1-C_3H_7I~(+?), 2-C_3H_7I~(+?), 1-C_4H_9I~(+?) and 2-C_4H_9I~(+?) radical cations were studied within the ?←X? absorption band. The photodissociation mass spectra within the range 13,600-15,900 cm~(-1) (1.68-1.97 eV) display only a simple cleavage of the C-I bond and formation of the corresponding alkyl ions. The resonant (1+1)-photodissociation spectra of C_2H_5I~(+?) and C_2D5I~(+?) show intense vibrational structure in the excited ? state. The thresholds for formation of the ? states of C_2H_5I+ and C_2D_5I~+ were estimated to be (13,278 ± 12) cm -1 (1.6462 ± 0.0014 eV) and (13,363 ± 12) cm~(-1)(1.6586 ± 0.0014 eV), respectively. Whereas a few resonant vibrational excitations could be identified with 1-C_3H_7I~(+?) and 1-C4H7I+, novibrational features were observable with 2-C_3H_7I~(+?) and 2-C_4H_9I~(+?). It is concluded that 1- and 2-iodoalkane radical cations do not rearrange, even under the conditions of electron ionisation used to generate the molecular ions.