No abstract

Articles you may be interested inPhotoelectron imaging of carbonyl sulfide cluster anions: Isomer coexistence and competition of excited-state decay mechanisms Photoelectron spectroscopy of gold-silver binary cluster anions ( Au n Ag m − ; 2n+m4) Electronic isomers in [( CO 2 ) n ROH ] − cluster anions. II. Ab initio calculations Photoelectron spectra of ͓(CO 2 ) nϪ1 ROH͔ Ϫ ͑RϭH and CH 3 ͒ with 2рnр7 have been measured at a photon energy of 4.66 eV. Analysis of the photoelectron band envelopes has revealed that the spectra of ͓(CO 2 ) nϪ1 H 2 O͔ Ϫ with 3рnр5 consist of two band components. The maximum of each component corresponds to the vertical detachment energy ͑VDE͒ of the relevant anionic species. In each spectrum the VDE values for the two components differ by Ϸ1 eV. For example, the ͓͑CO 2 ͒ 4 H 2 O͔ Ϫ spectrum is characterized by two VDE values of 2.63Ϯ0.04 and 3.71Ϯ0.06 eV. From the VDE difference, we conclude that the observed two components arise from isomers having different electronic structures, and that these ''electronic isomers'' can be designated as C 2 O 4 Ϫ •H 2 O͑CO 2 ͒ nϪ3 and CO 2 Ϫ •H 2 O͑CO 2 ͒ nϪ2 . Coexistence of electronic isomers occurs also in ͓(CO 2 ) nϪ1 CH 3 OH͔ Ϫ , but only at nϭ3. The ͓(CO 2 ) nϪ1 CH 3 OH͔ Ϫ anions with n 3 display photoelectron spectra composed of a single broad band, which corresponds to photodetachment from CO 2 Ϫ •CH 3 OH͑CO 2 ͒ nϪ2 structure. The CO 2 Ϫ •ROH͑CO 2 ͒ isomers (nϭ3) are found to be distinguishable from C 2 O 4 Ϫ •ROH by selective photodepletion at 532 nm during the time of flight in the mass spectrometer, implying that the two electronic isomers of ͓͑CO 2 ͒ 2 ROH͔ Ϫ coexist without interconversion. In contrast, it is revealed that ͓͑CO 2 ͒ 4 H 2 O͔ Ϫ (nϭ5) are fluctuating between C 2 O 4 Ϫ •H 2 O͑CO 2 ͒ 2 and CO 2 Ϫ •H 2 O͑CO 2 ͒ 3 structures. Based on these experimental findings, combined with results obtained by recent ab initio calculations, a possible isomerization mechanism operative in ͓(CO 2 ) nϪ1 ROH͔ Ϫ is proposed.