We have obtained the high-resolution threshold photoelectron （TPE） spectra of chlorobenzene C6HaCl （X1A1）, propargyl radical C3H3 （X2B1）, and allyl radical C3H5 （X2A1） by employing the vacuum ultraviolet （VUV...We have obtained the high-resolution threshold photoelectron （TPE） spectra of chlorobenzene C6HaCl （X1A1）, propargyl radical C3H3 （X2B1）, and allyl radical C3H5 （X2A1） by employing the vacuum ultraviolet （VUV） laser velocity-map-imaging-TPE （VUV-VMI-TPE） method. The photoelectron energy resolution of 1-2 cm^-1 observed for the VUV-VMI-TPE method is comparable to that achieved in VUV laser pulsed-field ionization-photoelectron （VUV-PFI-PE） measurements. Similar to VUV-PFI-PE measurements, the energy resolutions for VUV-VMI-photoelectron （VUV-VMI-PE） and VUV-VMI-TPE measurements are found to depend on the dc electric field F in V/cm used at the photoionization region for electron extraction. The decrease of the ionization thresholds of C6H5Cl and C3H3 observed as a function of F shows that the Stark shift correction for VUV-VMI-TPE measurements is governed by the formula -3.1√F in cm^-1, which is half of the classical prediction of -6.1v/F in cm^-1. We have also measured the VUV-VMI-PE spectra of C6H5Cl and C3H5 at VUV energies near their ionization thresholds. The cationic vibrational bands observed in the VUV-VMI-PE measurements were assigned to be the vibrational progression, nv7＋ （n=0-3）, for C3H＋. The higher experimental sensitivity and similar energy resolutions achieved in VUV-VMI-TPE compared to VUV-PFI-PE measurements make the VUV-VMI- TPE method an excellent alternative for high-resolution VUV-PFI-PE measurements.展开更多
The present review focused on selected, recent experimental progress of photodissociation dynamics of small molecules covering the vacuum ultraviolet (VUV) range from 6 eV to 20 eV. These advancements come about due t...The present review focused on selected, recent experimental progress of photodissociation dynamics of small molecules covering the vacuum ultraviolet (VUV) range from 6 eV to 20 eV. These advancements come about due to the available laser based VUV light sources along with the developments of advanced experimental techniques, including the velocitymap imaging (VMI), H-atom Rydberg tagging time-of-flight (HRTOF) techniques, as well as the two-color tunable VUV-VUV laser pump-probe detection method. The applications of these experimental techniques have allowed VUV photodissociation studies of many diatomic and triatomic molecules to quantum state-to-state in detail. To highlight the recent accomplishments, we have summarized the results on several important molecular species, including H2 (D2, HD), CO, N2, NO, O2, H2O (D2O, HOD), CO2, and N2O. The detailed VUV photodissociation studies of these molecules are of astrochemical and atmospheric relevance. Since molecular photodissociation initiated by VUV excitation is complex and is often governed by multiple electronic potential energy surfaces, the unraveling of the complex dissociation dynamics requires state-to-state cross section measurements. The newly constructed Dalian Coherent Light Source (DCLS), which is capable of generating coherent VUV radiation with unprecedented brightness in the range of 50-150 nm, promises to propel the photodissociation experiment to the next level.展开更多
基金This work was supported by the National Science Foundation under CHE-0910488 and CHE-1462172. C. Y. Ng also acknowledges the support by the Chemi- cal Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, （US） Department of Energy （DOE） under Contract No.DEFG02-02ER15306.
文摘We have obtained the high-resolution threshold photoelectron （TPE） spectra of chlorobenzene C6HaCl （X1A1）, propargyl radical C3H3 （X2B1）, and allyl radical C3H5 （X2A1） by employing the vacuum ultraviolet （VUV） laser velocity-map-imaging-TPE （VUV-VMI-TPE） method. The photoelectron energy resolution of 1-2 cm^-1 observed for the VUV-VMI-TPE method is comparable to that achieved in VUV laser pulsed-field ionization-photoelectron （VUV-PFI-PE） measurements. Similar to VUV-PFI-PE measurements, the energy resolutions for VUV-VMI-photoelectron （VUV-VMI-PE） and VUV-VMI-TPE measurements are found to depend on the dc electric field F in V/cm used at the photoionization region for electron extraction. The decrease of the ionization thresholds of C6H5Cl and C3H3 observed as a function of F shows that the Stark shift correction for VUV-VMI-TPE measurements is governed by the formula -3.1√F in cm^-1, which is half of the classical prediction of -6.1v/F in cm^-1. We have also measured the VUV-VMI-PE spectra of C6H5Cl and C3H5 at VUV energies near their ionization thresholds. The cationic vibrational bands observed in the VUV-VMI-PE measurements were assigned to be the vibrational progression, nv7＋ （n=0-3）, for C3H＋. The higher experimental sensitivity and similar energy resolutions achieved in VUV-VMI-TPE compared to VUV-PFI-PE measurements make the VUV-VMI- TPE method an excellent alternative for high-resolution VUV-PFI-PE measurements.
基金supported by the National Natural Science Foundation of China (No.21803072)the Program for Young Outstanding Scientists of Institute of Chemistry, Chinese Academy of Science (ICCAS)+2 种基金Beijing National Laboratory for Molecular Sciences (BNLMS)supported by the National Aeronautics and Space Administration Award #: 80NSSC18K0592National Science Foundation under CHE-1763319
文摘The present review focused on selected, recent experimental progress of photodissociation dynamics of small molecules covering the vacuum ultraviolet (VUV) range from 6 eV to 20 eV. These advancements come about due to the available laser based VUV light sources along with the developments of advanced experimental techniques, including the velocitymap imaging (VMI), H-atom Rydberg tagging time-of-flight (HRTOF) techniques, as well as the two-color tunable VUV-VUV laser pump-probe detection method. The applications of these experimental techniques have allowed VUV photodissociation studies of many diatomic and triatomic molecules to quantum state-to-state in detail. To highlight the recent accomplishments, we have summarized the results on several important molecular species, including H2 (D2, HD), CO, N2, NO, O2, H2O (D2O, HOD), CO2, and N2O. The detailed VUV photodissociation studies of these molecules are of astrochemical and atmospheric relevance. Since molecular photodissociation initiated by VUV excitation is complex and is often governed by multiple electronic potential energy surfaces, the unraveling of the complex dissociation dynamics requires state-to-state cross section measurements. The newly constructed Dalian Coherent Light Source (DCLS), which is capable of generating coherent VUV radiation with unprecedented brightness in the range of 50-150 nm, promises to propel the photodissociation experiment to the next level.
