Single-photon ionization of pyrene and anthracene giving trapped electrons in alkali-metal cation-exchanged zeolites X and Y: a direct time-resolved diffuse reflectance study

1991 ◽  
Vol 95 (2) ◽  
pp. 506-509 ◽  
Author(s):  
Kai Kong Iu ◽  
J. K. Thomas
Keyword(s):  
Alkali Metal ◽  
Metal Cation ◽  
Diffuse Reflectance ◽  
Single Photon ◽  
Alkali Metal Cation ◽  
Time Resolved ◽  
Trapped Electrons ◽  
Single Photon Ionization ◽  
Photon Ionization

Influence of alkali metal cations on the photoheterolysis of 9-cyclopropyl-9-fluorenol and the reactivity of the 9-cyclopropyl-9-fluorenyl cation in non-acidic zeolites

2003 ◽  
Vol 81 (6) ◽  
pp. 647-659 ◽  
Author(s):  
Melanie A O'Neill ◽  
Frances L Cozens
Keyword(s):  
Alkali Metal ◽  
Metal Cation ◽  
Diffuse Reflectance ◽  
Bond Cleavage ◽  
Alkali Metal Cation ◽  
Zeolite Framework ◽  
Time Resolved ◽  
Highly Sensitive ◽  
Cation Size ◽  
Acidic Zeolites

Alkali metal cation regulation of carbocation formation and reactivity in non-acidic zeolites is probed using the photoheterolysis reaction of 9-cyclopropyl-9-fluorenol. Nanosecond time-resolved diffuse reflectance is employed to directly observe the 9-cyclopropyl-9-fluorenyl cation as a transient species within the non-acidic zeolites. The efficiency of carbocation formation via photoheterolysis and the dynamics of other reaction pathways available to photoexcited 9-cyclopropyl-9-fluorenol are found to be strongly dependent on the zeolite alkali metal counterion. In particular, the yield of carbocation decreases with increasing counterion size in a manner consistent with the zeolite assisting the excited state C—O bond cleavage via Lewis acid catalysis involving the metal cation. Zeolite encapsulation is also found to modulate the ability of water and methanol to assist photoheterolysis. For instance, the influence of coadsorbed water on the photoheterolysis reaction within zeolites is found to be highly sensitive to the alkali metal cation. The rate constant for intrazeolite decay of the 9-cyclopropyl-9-fluorenyl cation increases significantly as the alkali metal cation size increases and as the Si–Al ratio decreases. These reactivity trends suggest that the intrazeolite decay of the 9-cyclopropyl-9-fluorenyl cation involves nucleophilic addition at the active site [Si-O-Al]– bridges of the zeolite framework. In addition, the reactivity of the 9-cyclopropyl-9-fluorenyl cation within alkali metal zeolites can be regulated by the co-inclusion of reagents such as methanol, water, and 1,1,1,3,3,3-hexafluoro-2-propanol.Key words: cation-exchanged zeolites, 9-cyclopropyl-9-fluorenyl cation, laser photolysis, reactivity.

scholarly journals Simulated and Experimental Time-Resolved Photoelectron Spectra of the Intersystem Crossing Dynamics in 2-Thiouracil

Molecules ◽  
2018 ◽  
Vol 23 (11) ◽  
pp. 2836 ◽  
Author(s):  
Sebastian Mai ◽  
Abed Mohamadzade ◽  
Philipp Marquetand ◽  
Leticia González ◽  
Susanne Ullrich
Keyword(s):  
Gas Phase ◽  
Single Photon ◽  
Photoelectron Spectra ◽  
Time Resolved ◽  
Single Photon Ionization ◽  
Biologically Relevant ◽  
Two Photon ◽  
Photon Ionization ◽  
Ionic States ◽  
Good Agreement

We report time-dependent photoelectron spectra recorded with a single-photon ionization setup and extensive simulations of the same spectra for the excited-state dynamics of 2-thiouracil (2TU) in the gas phase. We find that single-photon ionization produces very similar results as two-photon ionization, showing that the probe process does not have a strong influence on the measured dynamics. The good agreement between the single-photon ionization experiments and the simulations shows that the norms of Dyson orbitals allow for qualitatively describing the ionization probabilities of 2TU. This reasonable performance of Dyson norms is attributed to the particular electronic structure of 2TU, where all important neutral and ionic states involve similar orbital transitions and thus the shape of the Dyson orbitals do not strongly depend on the initial neutral and final ionic state. We argue that similar situations should also occur in other biologically relevant thio-nucleobases, and that the time-resolved photoelectron spectra of these bases could therefore be adequately modeled with the techniques employed here.

Conformational effect on the preferential binding of alkali metal cation with crown ether: A molecular level investigation

2009 ◽  
Vol 12 (1-3) ◽  
pp. 93-99 ◽  
Author(s):  
Sulagna De ◽  
Sk. Musharaf Ali ◽  
M.R.K. Shenoi ◽  
Sandip K. Ghosh ◽  
Dilip K. Maity
Keyword(s):  
Crown Ether ◽  
Alkali Metal ◽  
Metal Cation ◽  
Molecular Level ◽  
Alkali Metal Cation ◽  
Conformational Effect ◽  
Preferential Binding

Vacuum Ultraviolet Single-Photon Ionization Time-of-Flight Mass Spectrometer

2011 ◽  
Vol 39 (10) ◽  
pp. 1470-1475 ◽  
Author(s):  
Guo-Bin TAN ◽  
Wei GAO ◽  
Zheng-Xu HUANG ◽  
Yi HONG ◽  
Zhong FU ◽  
...  
Keyword(s):  
Mass Spectrometer ◽  
Vacuum Ultraviolet ◽  
Single Photon ◽  
Time Of Flight ◽  
Ionization Time ◽  
Single Photon Ionization ◽  
Flight Mass Spectrometer ◽  
Photon Ionization
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