The H atom production channels in the ultraviolet （UV） photochemistry of m-pyridyl radical （m-C5H4N） were investigated at excitation wavelengths from 224 nm to 248 nm by high-n Rydberg atom time-of-flight （HRTOF...The H atom production channels in the ultraviolet （UV） photochemistry of m-pyridyl radical （m-C5H4N） were investigated at excitation wavelengths from 224 nm to 248 nm by high-n Rydberg atom time-of-flight （HRTOF） technique. The photofragment yield （PFY） spectrum of the H atoms indicates a broad UV absorption feature near 234 nm. The product kinetic energy release is small; the average product kinetic energy at the wavelengths from 224 nm to 248 nm is 0.12 to 0.19 of the maximum excess energy （assuming the lowest energy product channel, H＋cyanovinylacetylene）. The product kinetic energy distributions are consistent with the H cyanovinylacetylene, H 3,4-pyridyne, and H 2,3-pyridyne product channels, with H cyanovinylacetylene as the main H-loss channel. The angular distributions of the H-atom products are isotropic. After the UV electronic excitation, the m-pyridyl radical undergoes internal conversion to the ground electronic state and then unimolecular dissoci-ation to the H cyanovinylacetylene, H 3,4-pyridyne, and H 2,3-pyridyne products. The dissociation mechanism of the m-pyridyl radical is similar to that of the o-pyridyl radical reported in the early study.展开更多
The recen tly cons true ted cryogenic cylindrical ion trap velocity map imaging spectrometer(CIT-VMI)has been upgraded for coincidence imaging of both ionic and neutral photofragments from photodissociation of ionic s...The recen tly cons true ted cryogenic cylindrical ion trap velocity map imaging spectrometer(CIT-VMI)has been upgraded for coincidence imaging of both ionic and neutral photofragments from photodissociation of ionic species.The prepared ions are cooled down in a homemade cryogenic cylindrical ion trap and then extracted for photodissociation experiments.Wi th the newly designed elec trie fields for extraction and acceleration,the ion beam can be accelerated to more than 4500 eV,which is necessary for velocity imaging of the neutral photofragments by using the position-sensitive imaging detect or.The setup has been tested by the 355 nm pho todissocia tion dynamics of the argon dimer cat ion(Ar2+).From the recorded experimen tal images of both neu tral Ar and ionic Ar+fragments,we interpret velocity resolutions of△v/vu4.6%for neutral fragments,and△v/vul.5%for ionic fragments,respectively.展开更多
基金This work was supported by the US National Science Foundation （CHE-1214157）. Jasmine Minor acknowledges the support from the UC Riverside HSI-STEM Summer Bridge to Research Program and the Summer Research in Science and Engineering [RISE] Program.
文摘The H atom production channels in the ultraviolet （UV） photochemistry of m-pyridyl radical （m-C5H4N） were investigated at excitation wavelengths from 224 nm to 248 nm by high-n Rydberg atom time-of-flight （HRTOF） technique. The photofragment yield （PFY） spectrum of the H atoms indicates a broad UV absorption feature near 234 nm. The product kinetic energy release is small; the average product kinetic energy at the wavelengths from 224 nm to 248 nm is 0.12 to 0.19 of the maximum excess energy （assuming the lowest energy product channel, H＋cyanovinylacetylene）. The product kinetic energy distributions are consistent with the H cyanovinylacetylene, H 3,4-pyridyne, and H 2,3-pyridyne product channels, with H cyanovinylacetylene as the main H-loss channel. The angular distributions of the H-atom products are isotropic. After the UV electronic excitation, the m-pyridyl radical undergoes internal conversion to the ground electronic state and then unimolecular dissoci-ation to the H cyanovinylacetylene, H 3,4-pyridyne, and H 2,3-pyridyne products. The dissociation mechanism of the m-pyridyl radical is similar to that of the o-pyridyl radical reported in the early study.
基金This work was supported by the National Key R&D Program of China(No.2017YFA0303502)the National Natural Science Foundation of China(No.21773221 and No.21827804)the Fundamental Research Funds for the Central Universities of China(No.WK2340000078).
文摘The recen tly cons true ted cryogenic cylindrical ion trap velocity map imaging spectrometer(CIT-VMI)has been upgraded for coincidence imaging of both ionic and neutral photofragments from photodissociation of ionic species.The prepared ions are cooled down in a homemade cryogenic cylindrical ion trap and then extracted for photodissociation experiments.Wi th the newly designed elec trie fields for extraction and acceleration,the ion beam can be accelerated to more than 4500 eV,which is necessary for velocity imaging of the neutral photofragments by using the position-sensitive imaging detect or.The setup has been tested by the 355 nm pho todissocia tion dynamics of the argon dimer cat ion(Ar2+).From the recorded experimen tal images of both neu tral Ar and ionic Ar+fragments,we interpret velocity resolutions of△v/vu4.6%for neutral fragments,and△v/vul.5%for ionic fragments,respectively.
