Photon-induced dissociation pathways of thymine are investigated with vacuum ultraviolet photoionization mass spectrometry and theoretical calculations. The photoionization mass spectra of thymine at different photon ...Photon-induced dissociation pathways of thymine are investigated with vacuum ultraviolet photoionization mass spectrometry and theoretical calculations. The photoionization mass spectra of thymine at different photon energy are measured and presented. By selecting suitable photon energy, exclusively molecular ion m/z=126 is obtained. At photon energy of 12.0 eV, the major ionic fragments at m/z=98, 97, 84, 83, 70, and 55 are obtained, which are assigned to C4H6N2O＋, C4H5N2O＋, C3H4N2O＋ （or C4H6NO＋）, C4H5NO＋, C2NO2＋, and C3H5N＋, respectively. With help of theoretical calculations, the detailed dissociation pathways of thymine at low energy are well established.展开更多
The effect of solvation on the conformation of acetylene has been studied by adding one water molecule at a time. Quantum chemical calculations of the n＋ （C2H2）（H2O）n （n=1-5） clusters indicate that the H2O mole...The effect of solvation on the conformation of acetylene has been studied by adding one water molecule at a time. Quantum chemical calculations of the n＋ （C2H2）（H2O）n （n=1-5） clusters indicate that the H2O molecules prefer to form the OH...Tr interaction rather than the CH...O interaction. This solvation motif is different from that of neutral （C2H2）（H2O）n （n=1-4） clusters, in which the H2O molecules prefer to form the CH...O and OH...C Hbonds. For the H＋（C2H2）（H2O）n cationic clusters, the first solvation shell consists of one ring structure with two OH...Tr H-bonds and three water molecules, which is completed at n=4. Simulated infrared spectra reveal that vibrational frequencies of OH... H-bonded O-H stretching afford a sensitive probe for exploring the solvation of acetylene by protonated water molecules. Infrared spectra of the H＋ （C2H2）（H2O）n （n=1-5） clusters could be readily measured by the infrared photodissociation technique and thus provide useful information for the understanding of solvation processes.展开更多
The boron carbonyl cation complexes B（CO）3＋, B（CO）4＋ and B2（CO）4＋ are studied by infrared photodissociation spectroscopy and theoretical calculations. The B（CO）4＋ ions are characterized to be very weakly b...The boron carbonyl cation complexes B（CO）3＋, B（CO）4＋ and B2（CO）4＋ are studied by infrared photodissociation spectroscopy and theoretical calculations. The B（CO）4＋ ions are characterized to be very weakly bound complexes involving a B（CO）3＋ core ion, which is predicted to have a planar D3h structure with the central boron retaining the most favorable 8-electron configuration. The B2（C0）4＋ cation is determined to have a planar D2h structure involving a B-B one and half bond. The analysis of the B-CO interactions with the EDA- NOCV method indicates that the OC→B cr donation is stronger than the B-＋CO π back donation in both ions.展开更多
The mass-selected infrared photodissociation (IRPD) spectroscopy was utilized to investigate the interactions of cationic cobalt with carbon dioxide molecules. Quantum chemical calculations were performed on the [Co(C...The mass-selected infrared photodissociation (IRPD) spectroscopy was utilized to investigate the interactions of cationic cobalt with carbon dioxide molecules. Quantum chemical calculations were performed on the [Co(CO2)n]^+ clusters to identify the structures of the low-lying isomers and to assign the observed spectral features. All the [Co(CO2)n]^+(n=2-6) clusters studied here show resonances near the CO2 asymmetric stretch of free CO2 molecule. Experimental and calculated results indicate that the CO2 molecules are weakly bound to the Co+ cations in an end-on con guration via a charge-quadrupole electrostatic interaction. The present IRPD spectra of [Co(CO2)n]^+ clusters have been compared to those of Ar-tagged species ([Co(CO2)n]^+-Ar), which would provide insights into the tagging effect of rare gas on the weakly-bounded clusters.展开更多
Infrared photodissociation spectroscopy of mass-selected[MO(CO2)n]^+(M=Sc,Y,La)complexes indicates that the conversion from the solvated structure into carbonate one can be achieved by the ScO^+ cation at n=5 and by t...Infrared photodissociation spectroscopy of mass-selected[MO(CO2)n]^+(M=Sc,Y,La)complexes indicates that the conversion from the solvated structure into carbonate one can be achieved by the ScO^+ cation at n=5 and by the YO^+ cation at n=4,while only the solvated structures are observed for the LaO^+ cation.These findings suggest that both the ScO^+ and YO^+cations are able to fix CO2 into carbonate.Quantum chemical calculations are performed on[MO(CO2)n]^+ to identify the structures of the low-lying isomers and to assign the observed spectral features.Theoretical analyses show that the[YO(CO2)n]^+ complex has the smallest barrier for the conversion from the solvated structure into carbonate one,while[LaO(CO2)n]^+ exhibits the largest conversion barrier among the three metal oxide cations.The present system affords a model in clarifying the effect of different metals in catalytic CO2 transformation at the molecular level.展开更多
Calculation of a variation of discrete Fourier transform.Chrestenson spectraof functions of n indeterminates over integer modulo m(composite integer),is con-sidered.Based on sparse matrix decomposition,two fast algori...Calculation of a variation of discrete Fourier transform.Chrestenson spectraof functions of n indeterminates over integer modulo m(composite integer),is con-sidered.Based on sparse matrix decomposition,two fast algorithms with complexityO(mnn∑ri=1pi)are given to calculate the Chrestenson spectra,where p1p2…p2 is theprime factor decomposition of m.展开更多
基金This work was supported by the Chinese Academy of Sciences and the National Natural Science Foundation of China （No.10805047）. Authors appreciate the kind help from Dr. Yang Pan in experiments.
文摘Photon-induced dissociation pathways of thymine are investigated with vacuum ultraviolet photoionization mass spectrometry and theoretical calculations. The photoionization mass spectra of thymine at different photon energy are measured and presented. By selecting suitable photon energy, exclusively molecular ion m/z=126 is obtained. At photon energy of 12.0 eV, the major ionic fragments at m/z=98, 97, 84, 83, 70, and 55 are obtained, which are assigned to C4H6N2O＋, C4H5N2O＋, C3H4N2O＋ （or C4H6NO＋）, C4H5NO＋, C2NO2＋, and C3H5N＋, respectively. With help of theoretical calculations, the detailed dissociation pathways of thymine at low energy are well established.
基金This work was supported by the National Natural Science Foundation of China （No.21273232 and No.21327901） and the Key Research Program of the Chinese Academy of Science （No.KGZD-EW-T05）. Ling Jiang acknowledges Hundred Talents Program of Chinese Academy of Sciences and Collaborative Innovation Center of Chemistry for Energy and Materials.
文摘The effect of solvation on the conformation of acetylene has been studied by adding one water molecule at a time. Quantum chemical calculations of the n＋ （C2H2）（H2O）n （n=1-5） clusters indicate that the H2O molecules prefer to form the OH...Tr interaction rather than the CH...O interaction. This solvation motif is different from that of neutral （C2H2）（H2O）n （n=1-4） clusters, in which the H2O molecules prefer to form the CH...O and OH...C Hbonds. For the H＋（C2H2）（H2O）n cationic clusters, the first solvation shell consists of one ring structure with two OH...Tr H-bonds and three water molecules, which is completed at n=4. Simulated infrared spectra reveal that vibrational frequencies of OH... H-bonded O-H stretching afford a sensitive probe for exploring the solvation of acetylene by protonated water molecules. Infrared spectra of the H＋ （C2H2）（H2O）n （n=1-5） clusters could be readily measured by the infrared photodissociation technique and thus provide useful information for the understanding of solvation processes.
基金The work was supported by the Ministry of Sci- ence and Technology of China （No.2013CB834603） and the National Natural Science Foundation of China （No.21173053 and No.21433005）.
文摘The boron carbonyl cation complexes B（CO）3＋, B（CO）4＋ and B2（CO）4＋ are studied by infrared photodissociation spectroscopy and theoretical calculations. The B（CO）4＋ ions are characterized to be very weakly bound complexes involving a B（CO）3＋ core ion, which is predicted to have a planar D3h structure with the central boron retaining the most favorable 8-electron configuration. The B2（C0）4＋ cation is determined to have a planar D2h structure involving a B-B one and half bond. The analysis of the B-CO interactions with the EDA- NOCV method indicates that the OC→B cr donation is stronger than the B-＋CO π back donation in both ions.
基金supported by the National Natural Science Foundation of China(No.21327901,No.21503222,No.21673231,and No.21688102)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB17000000)China Postdoctoral Science Foundation(No.2018M641718 and No.2018M641719)
文摘The mass-selected infrared photodissociation (IRPD) spectroscopy was utilized to investigate the interactions of cationic cobalt with carbon dioxide molecules. Quantum chemical calculations were performed on the [Co(CO2)n]^+ clusters to identify the structures of the low-lying isomers and to assign the observed spectral features. All the [Co(CO2)n]^+(n=2-6) clusters studied here show resonances near the CO2 asymmetric stretch of free CO2 molecule. Experimental and calculated results indicate that the CO2 molecules are weakly bound to the Co+ cations in an end-on con guration via a charge-quadrupole electrostatic interaction. The present IRPD spectra of [Co(CO2)n]^+ clusters have been compared to those of Ar-tagged species ([Co(CO2)n]^+-Ar), which would provide insights into the tagging effect of rare gas on the weakly-bounded clusters.
基金supported by the National Natural Science Foundation of China (No.21327901,No.21673231,No.21673234,and No.21688102)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB17000000)K. C. Wong Education Foundation.
文摘Infrared photodissociation spectroscopy of mass-selected[MO(CO2)n]^+(M=Sc,Y,La)complexes indicates that the conversion from the solvated structure into carbonate one can be achieved by the ScO^+ cation at n=5 and by the YO^+ cation at n=4,while only the solvated structures are observed for the LaO^+ cation.These findings suggest that both the ScO^+ and YO^+cations are able to fix CO2 into carbonate.Quantum chemical calculations are performed on[MO(CO2)n]^+ to identify the structures of the low-lying isomers and to assign the observed spectral features.Theoretical analyses show that the[YO(CO2)n]^+ complex has the smallest barrier for the conversion from the solvated structure into carbonate one,while[LaO(CO2)n]^+ exhibits the largest conversion barrier among the three metal oxide cations.The present system affords a model in clarifying the effect of different metals in catalytic CO2 transformation at the molecular level.
基金Supported by the National Natural Science Foundation of China(90104034)the 863 Program(2002AA141020)the Guangdong Provincial Natural Science Foundation(990336)
文摘Calculation of a variation of discrete Fourier transform.Chrestenson spectraof functions of n indeterminates over integer modulo m(composite integer),is con-sidered.Based on sparse matrix decomposition,two fast algorithms with complexityO(mnn∑ri=1pi)are given to calculate the Chrestenson spectra,where p1p2…p2 is theprime factor decomposition of m.
