Dissociative photoionization of CH3C(O)CH2 to C2H5+

VUV-Induced Photodissociation of the Chloroacetone Molecule Studied by Photoelectron-Photoion Coincidence Spectroscopy

“…We assign the latter to the ethyl cation (C 2 H 5 + ), which may be formed through the bond cleavage between the ethyl and the CO groups from the propanoyl cation (m/z 57), as in reaction 11. A similar mechanism for the formation of this cation was also proposed by Alligood et al 10…”

“…Foffani et al have reported some dissociation channels from this molecule using a magnetic sector mass spectrometer and a Nier-type ion source. Other reports have studied dissociation reactions from chloroacetone at some predefined energies. − Briefly, Alligood et al − have studied the bond photofission of the chloroacetone neutral molecule at 193 nm by means of crossed-laser molecular beam scattering and velocity map imaging experiments and reported that the C–Cl bond fission corresponds to the most relevant dissociation channel of the molecule, as well as studies on the dissociation of the CH 3 COCH 2 radical into the ketene and methyl products and its dissociative photoionization to C 2 H 5 + and CO species. Waschewsky et al and Kitchen et al investigated the photodissociation of the chloroacetone at 308 nm by employing the crossed-laser molecular beam scattering technique and indicated that the C–Cl bond cleavage is favored in the more energetic trans conformer of the neutral molecule and is therefore temperature dependent.…”

Analyzing velocity map images to distinguish the primary methyl photofragments from those produced upon C–Cl bond photofission in chloroacetone at 193 nm

“…Although stable radicals were not present at parent m/e = 57 (CH 3 C(O)CH 2 + ) in either the scattering or imaging apparatuses, we were able to confirm the validity of the results obtained with this impulsive model by comparing with the signal observed at daughter mass-to-charge ratios -the signal observed at m/e = 42 (COCH 2 + ) and at m/e = 15 (CH 3 + ) in the scattering apparatus with 200 eV electron bombardment ionization, 7 and with data taken at m/e = 29 (C 2 H 5 + ) in the imaging apparatus with 10.5 eV photoionization. 14 The results from this impulsive model revealed that roughly 77.8% of the CH 3 C(O)CH 2 radicals that were formed from primary C-Cl bond photofission were stable to subsequent dissociation to CH 3 and ketene. The other 22.2% were formed with vibrational energies above the dissociation barrier out to CH 3 + ketene; those products were detected at m/e = 15 (CH 3 + ) and at m/e = 42 (COCH 2 + ), respectively.…”

“…The velocity map imaging apparatus used in this work has been described previously; [9][10][11][12][13] the relevant experimental conditions have also been detailed in our previous work on this system. 7,14 We expand the molecular beam, composed of the vapor pressure of chloroacetone seeded in He to a total backing pressure of 400 Torr, through a pulsed valve; we heat the nozzle, which has a 0.8 mm diameter, to 80 • C. After passing through a skimmer, the molecules are photodissociated with a vertically polarized 193.3 nm beam.…”

“…The experimental details relevant to this system, both experimental conditions and defined apparatus parameters, have been described previously. 7,14 We expand the molecular beam, composed of chloroacetone seeded in He to a total stagnation pressure of 400 Torr, through a continuous (not pulsed) nozzle. The nozzle has a 0.15 mm diameter, and we heat it to 180 • C. The molecular beam passes through two skimmers before it enters the main chamber, where it intersects the output of a 193.3 nm excimer laser.…”