A Vacuum Ultraviolet Photoionization Mass Spectrometric Study of Acetone

Abstract

The photoionization and dissociative photoionization of acetone have been studied at the photon energy range of 8-20 eV. Photoionization efficiency spectra for ions CH3COCH3+, CH3+, C2H3+, C3H3+, C3H5+, CH(2-)CO+, CH3CO+, C3H4O+, and CH3COCH2+ have been measured. In addition, the energetics of the dissociative photoionization has been examined by ab initio Gaussian-3 (G3) calculations. The computational results are useful in establishing the dissociation channels near the ionization thresholds. With the help of G3 results, the dissociation channels for the formation of the fragment ions CH3CO+, CH2CO+, CH3+, C3H3+, and CH3COCH2+ have been established. The G3 results are in fair to excellent agreement with the experimental data.

A multiphoton ionization study of acetone using time-of-flight mass spectrometry

“…The photoionization of acetone and dissociation of the acetone cation, CH 3 COCH 3 + , have been reported previously by several groups [16][17][18][19][20][21][22][23][24][25][26][27][28][29]. The unimolecular dissociation of acetone cation has been investigated using photoionization efficiency and photoelectron-photoion coincidence (PEPICO) spectra [16][17][18][19][20]22] and various theories [27][28][29]. The following dissociation channels have been observed in the low internal energy region of the acetone cation: Cant et al [16] reported that: (a) at 0-0.3 eV above the ionization threshold (9.7 eV) of acetone only the parent ions were observed; (b) CH 3 CO + appeared at 10.3 eV; (c) the CH 3 + product channel was initiated at approximately 13 eV; (d) at the ionization energy to the first excited state of acetone cation, ~12 eV, some parent ions were observed along with dominant CH 3 CO + fragments; and (e) the average kinetic energy releases of CH 3 CO + and CH 3 + were found to vary linearly with the internal energy of the acetone cation in the low energy region.…”

“…The vibra-*Corresponding author (email: zxf7002@mail.ahnu.edu.cn) tional assignments in the 3p Rydberg state were deduced from polarization-selected two-and three-photon resonance enhanced multiphoton ionization (REMPI) spectroscopy [7,8,10,12,14,15]. The photoionization of acetone and dissociation of the acetone cation, CH 3 COCH 3 + , have been reported previously by several groups [16][17][18][19][20][21][22][23][24][25][26][27][28][29]. The unimolecular dissociation of acetone cation has been investigated using photoionization efficiency and photoelectron-photoion coincidence (PEPICO) spectra [16][17][18][19][20]22] and various theories [27][28][29].…”

“…Solid lines represent linear fittings. 10.52 eV [17,19], which is 0.83 eV above the threshold ionization energy of acetone. This, along with the photoionization efficiency curves and breakdown diagrams of acetone [16,19,20], indicates that the vibrational ground state and low vibrationally excited states of the acetone cation are stable.…”

“…The ionization potential (IP) of CH 3 COCH 3 and appearance potential (AP) of CH 3 CO + were later refined. The IP of CH 3 COCH 3 and AP of CH 3 CO + were determined to be (9.694 ± 0.006) eV and (10.52 ± 0.02) eV, respectively, from molecular beam photoionization studies of acetone [17], and (9.69 ± 0.02) eV and (10.49 ± 0.02) eV, respectively, from vacuum ultraviolet (VUV) photoionization efficiency spectra of CH 3 COCH 3 + and CH 3 CO + [19]. PEPICO measurements showed the AP of CH 3 + in the CH 3 CO + CH 3 + channel was 13.0 eV [16], while the AP of CH 3 + corresponding to the dissociation of CH 3 COCH 3 + into CH 3 + , CH 3 , and CO was determined to be (14.41 ± 0.04) eV [19].…”

Suppression of the Methyl Radical Loss from Acetone Cation within (CH3COCH3)n{CH3COCH3}+Clusters

“…6 Appearance potential of the methyl radical loss from the acetone cation (CH 3 COCH 3 · + → CH 3 CO + + CH 3 ·) is 10.563 eV. 6 Recently, rich dissociation processes of the acetone cation in the vacuum ultraviolet (VUV) energy region have been investigated by threshold photoelectron photoion coincidence (TPEPICO) spectroscopy, 6 VUV photoabsorption and ionization using synchrotron radiation, 7,8 and electron impact ionization. 9 The dissociative ionization of acetone above the threshold energy of the methyl radical loss from the acetone cation was also observed in the previous multiphoton ionization (MPI) experiments.…”