Dynamics of the KrF* Laser Multiphoton Dissociation of a Series of Arene Chromium Tricarbonyls

1988 ◽  
Vol 131 ◽  
Author(s):  
George W. Tyndall ◽  
Robert L. Jackson
Keyword(s):  
Gas Phase ◽  
Excited States ◽  
Dissociation Process ◽  
Parent Molecule ◽  
Electronically Excited ◽  
Arene Ligand ◽  
Multiphoton Dissociation ◽  
Sequential Absorption ◽  
The One ◽  
Direct Dissociation

ABSTRACTThe KrF* (248 nim) laser multiphoton dissociation (MPD) of a series of (arene)chromium tricarbonyls has been investigated in the gas-phase using emission spectroscopy to detect the excited state photoproducts. In the MPD of all compounds studied, chromium atoms are formed in a variety of electronically excited states via a two-channel dissociation mechanism. The predominant pathway for formation of the ground electronic state and the lowest excited states is by a sequential absorption/fragmentation process, where the product of the one-photon dissociation of the parent molecule absorbs an additional photon and dissociates to Cr(I). The higher energy Cr(I) states are formed exclusively by a direct dissociation process, where the parent absorbs multiple photons prior to dissociation. The distribution of excited chromium atoms formed in the direct channel is statistical for all compounds studied and is independent of the nature of the arene ligand. In contrast, the distribution of Cr(I) states formed via the sequential dissociation channel is strongly dependent on the vibrational density of states in the arene ligand.

Excitation and polarization analysis of the OD fragment radiation produced by dissociative electron impact on D2O

1982 ◽  
Vol 60 (8) ◽  
pp. 1168-1175 ◽  
Author(s):  
Kurt Becker ◽  
Günther Schulz
Keyword(s):  
Electron Impact ◽  
Time Scale ◽  
The Other ◽  
Polarization Analysis ◽  
Rotational Period ◽  
Dissociation Process ◽  
Parent Molecule ◽  
Dissociation Dynamics ◽  
Electronically Excited ◽  
Normal Water

The formation of electronically excited OD(A2Σ+) radicals following dissociative electron impact on D2O has been studied and a comparison with the H2O/OH (A2Σ+) dissociation system is made. Measurements of excitation functions reveal that the dissociation paths are largely unaffected by the deuteration of the parent molecule and even the weighting of the different dissociation channels leading to respectively slowly and rapidly rotating OD radicals is similar to the H2O dissociation process. On the other hand, the level of polarization of OD as compared with OH fragment radiation is found to be reduced by roughly a factor of 3. This may be explained in terms of an enhanced ratio of lifetime to rotational period for the parent D2O states. Thus the dissociation dynamics, i.e., the time scale between excitation and fragmentation, is demonstrated to react very sensitively when normal water is replaced by its deuterated specimen.

Excited-Atom Production by Electron Bombardment of Alkali-Halides

1986 ◽  
Vol 75 ◽  
Author(s):  
R. E. Walkup ◽  
Ph. Avouris ◽  
A. P. Ghosh
Keyword(s):  
Gas Phase ◽  
Excited States ◽  
Ground State ◽  
Excited Atom ◽  
Alkali Halides ◽  
Electron Bombardment ◽  
Secondary Electrons ◽  
Excited Atoms ◽  
Positive Ions ◽  
Electronically Excited

AbstractWe present experimental results which suggest a new mechanism for the production of excited atoms and ions by electron bombardment of alkali-halides. Doppler shift measurements show that the electronically excited atoms have a thermal velocity distribution in equilibrium with the surface temperature. Measurements of the absolute yield of excited atoms, the distribution of population among the excited states, and the dependence of yield on incident electron current support a model in which excited atoms are produced by gas-phase collisions between desorbed ground-state atoms and secondary electrons. Similarly, gas-phase ionization of ground-state neutrals by secondary electrons accounts for a substantial portion of the positive ions produced by electron bombardment of alkali-halides.

STUDY OF THE S1 AND S2 EXCITED STATES OF GAS-PHASE PROTONATED SCHIFF BASE RETINAL CHROMOPHORES IN ONE AND TWO PHOTON ABSORPTION

2011 ◽  
Vol 10 (02) ◽  
pp. 121-132 ◽  
Author(s):  
YUANZUO LI ◽  
PENG SONG ◽  
YING SHI ◽  
YONG DING ◽  
FENGJIE ZHOU ◽  
...  
Keyword(s):  
Schiff Base ◽  
Excited State ◽  
Charge Transfer ◽  
Gas Phase ◽  
Excited States ◽  
Density Functional ◽  
Three Dimensional ◽  
Photon Absorption ◽  
Two Photon ◽  
The One

The S1 and S2 excited states of gas-phase protonated Schiff base retinal chromophores in the one- and two-photon absorptions (TPAs) are investigated with time-dependent density functional theory. In one-photon absorption, the two-dimensional (2D) site and three-dimensional (3D) cube representations reveal that S1 and S2 excited states of gas-phase protonated Schiff base retinal chromophores are all charge transfer excited states. To better study the weak S2 excited states of gas-phase protonated Schiff base retinal chromophores, we investigated theoretically excited state properties of them in TPA. For 11-cis dimethyl retinal, it is found that the cross section of S2 excited state is 51.04 GM in PTA, which is only slightly smaller than that of S1 (77.04 GM) in TPA. Therefore, the S2 excited state of 11-cis dimethyl retinal can be clearly observed in TPA experiment. The 2D site and 3D cube representations reveal that electronic transition from S1 to S2 excited state of gas-phase protonated Schiff base retinal chromophores in TPA are also of charge transfer character.

Mercury-photosensitized reactions in the presence of CO: decomposition of ethylenimine

1967 ◽  
Vol 45 (14) ◽  
pp. 1685-1691 ◽  
Author(s):  
A. Jones ◽  
F. P. Lossing
Keyword(s):  
Excited States ◽  
Cross Sections ◽  
Dissociation Process ◽  
Decomposition Products ◽  
Electronically Excited ◽  
Co Addition ◽  
A Minor ◽  
Triplet Excited States ◽  
Direct Attack ◽  
Primary Interaction

The effect of CO addition on a number of Hg(3P1) photosensitized decompositions, under conditions of incomplete quenching, has been investigated. Compounds having large quenching cross sections (i.e. those presumably decomposing through formation of triplet excited states) have enhanced rates of decomposition in the presence of CO. Those having small cross sections (i.e. those for which the primary interaction is presumably the direct attack of Hg(3P1) atom on a C—H bond) show no enhancement. This difference in behavior, which is interpreted in terms of activation by a HgCO* complex, suggests that CO addition under the appropriate conditions can be used to decide whether or not certain decomposition products aries from an electronically excited precursor. For example, the effect of CO on the sensitized decomposition of ethylenimine indicates that the major dissociation process to form C2H4 and the NH radical proceeds by way of an electronically excited precursor, while a minor process (5%) to form [Formula: see text] radical and a H-atom does not. Some results on the sensitized decomposition of formaldehyde are also discussed.

scholarly journals Dynamics of electronically excited states in the eumelanin building block 5,6-dihydroxyindole

2019 ◽  
Vol 21 (15) ◽  
pp. 8152-8160 ◽  
Author(s):  
Stuart W. Crane ◽  
Omair Ghafur ◽  
Thomas Y. Cowie ◽  
Anita G. Lindsay ◽  
James O. F. Thompson ◽  
...  
Keyword(s):  
Gas Phase ◽  
Excited States ◽  
Thermal Desorption ◽  
Building Block ◽  
Electronically Excited States ◽  
Ultraviolet Excitation ◽  
Phase Study ◽  
Electronically Excited ◽  
Adiabatic Dynamics

Laser-based thermal desorption facilitates the first gas-phase study of ultrafast non-adiabatic dynamics operating in 5,6-dihydroxyinole following ultraviolet excitation.

UV Multiphoton Dissociation of Group VIB Hexacarbonyls and Derivatives

1986 ◽  
Vol 75 ◽  
Author(s):  
George W. Tyndall ◽  
Robert L. Jackson
Keyword(s):  
Gas Phase ◽  
Metal Atom ◽  
Pressure Dependence ◽  
Emission Intensity ◽  
Buffer Gas ◽  
Two Photon ◽  
Metal Atoms ◽  
Electronically Excited ◽  
Multiphoton Dissociation ◽  
Sequential Processes

AbstractFormation of electronically excited metal atoms via excimer laser multiphoton dissociation of Cr(CO)6, C6H6Cr(CO)3, and Mo(CO)6 has been examined in the gas phase. The dissociation mechanism was studied by determining the laserfluence- dependence and buffer-gas-pressure dependence of the metal atom emission intensity. Each of these species was found to form metal atoms via two-photon and three-photon dissociation processes. The data suggest that dissociation occurs by both direct and sequential processes.

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