scholarly journals A Simultaneous Photofragment Spectroscopy Measurement of Rovibronic and Translational Excitation in the CH3l A–Band Photodissociation System

1988 ◽  
Vol 9 (4-6) ◽  
pp. 339-358 ◽  
Author(s):  
John F. Black ◽  
Ivan Powis
Keyword(s):  
Methyl Iodide ◽  
Iodine Atom ◽  
Electronic Excitation ◽  
Multiphoton Ionization ◽  
Spatial Distributions ◽  
Initial Surface ◽  
Rotational Excitation ◽  
Methyl Radical ◽  
Specific Detection ◽  
Dissociation Dynamics

The methyl iodide A-band photodissociation is investigated using a photofragment time-of-flight technique coupled with state specific detection of either the iodine atom or methyl radical dissociation products by multiphoton ionization. The method is quite general and allows the fragments' velocity and spatial distributions to be determined simultaneously with their rotational, vibrational and electronic excitation. It is shown that methyl product from two competing dissociation channels, one direct, the other necessitating an initial surface crossing, can be clearly distinguished by virtue of the characteristic translational excitation in each. The different rotational excitation which is observed in these two channels is discussed in terms of the dissociation dynamics in the methyl iodide A-band continuum.

Collision-induced dissociation dynamics in O2++Ne(Ar) collisions: The role of electronic excitation

2000 ◽  
Vol 113 (19) ◽  
pp. 8561-8566 ◽  
Author(s):  
Rainer A. Dressler ◽  
Yu-hui Chiu ◽  
Dale J. Levandier ◽  
C. Y. Ng
Keyword(s):  
Electronic Excitation ◽  
Collision Induced Dissociation ◽  
Dissociation Dynamics

scholarly journals Femtosecond real-time probing of reactions. XIV. Rydberg states of methyl iodide

1994 ◽  
Vol 72 (3) ◽  
pp. 947-957 ◽  
Author(s):  
Hua Guo ◽  
Ahmed H. Zewail
Keyword(s):  
Methyl Iodide ◽  
Theoretical Calculations ◽  
Bond Cleavage ◽  
Isotope Effects ◽  
Rydberg States ◽  
Chem Phys ◽  
Two Dimensions ◽  
Special Focus ◽  
Methyl Radical ◽  
Valence States

The elementary reaction dynamics of methyl iodide in two Rydberg states leading to an iodine and a methyl radical occur on the femtosecond time scale (M.H. Janssen, M. Dantus, H. Guo, and A.H. Zewail. Chem. Phys. Lett. 214, 281 (1993)). In this article, we consider the dynamics of this elementary process which involves both the Rydberg and valence states. Direct comparisons are made between theory and experiment with special focus on the following observations: large isotope effects, mode dependence of the predissociation rates, and coherence effects. The quantal molecular dynamics in two-dimensions show that the initial wave packet motion occurs along a vibrational mode involving the light atoms accompanied by transitions from the Rydberg state to the repulsive state; subsequent dynamics on the dissociative state lead to the C—I bond cleavage. The theoretical calculations also give the decay behavior of the Rydberg states with lifetimes in agreement with those observed in the femtosecond experiments. Moreover, the large isotope effect in observed predissociation rates of CH3I and CD3I has been successfully reproduced by the same model. The two-dimensional dynamics underscore the shortcomings of a one-dimensional picture in which the C—I serves as the sole reaction coordinate. The model presented here offers a viable mechanism for the dynamics of these Rydberg states.

Non-adiabatic photodissociation dynamics of BrCl

1994 ◽  
Vol 72 (3) ◽  
pp. 758-761 ◽  
Author(s):  
Jianying Cao ◽  
Hans-Peter Loock ◽  
Charles X.W. Qian
Keyword(s):  
Laser Radiation ◽  
Potential Energy ◽  
Multiphoton Ionization ◽  
Branching Ratio ◽  
Tunable Laser ◽  
Branching Ratios ◽  
Excitation Wavelength ◽  
Dissociation Dynamics ◽  
Adiabatic Transitions ◽  
Insight Into

Nozzle-cooled BrCl was excited with tunable laser radiation at selected wavelengths between 389 and 500 nm. The chlorine atomic fragments in their Cl*(2P1/2) and Cl(2P3/2) state were stated-selectively probed by resonance-enhanced multiphoton ionization. The branching ratio (Cl*/(Cl + Cl*)) was measured as a function of the excitation wavelength. The relative Cl* yield reaches a maximum at around λphot = 460 nm. Decomposition of these branching ratios into Cl and Cl* photofragment yield spectra provides insight into the BrCl B-state 3П(0+) non-adiabatic dissociation dynamics. Our results suggest that the dissociation mechanism involves non-adiabatic transitions among 0+ potential energy curves.

Chirped pulse multiphoton ionization of nitrogen: Control of selective rotational excitation in N2+(B Σ2u+)

2009 ◽  
Vol 130 (24) ◽  
pp. 244313 ◽  
Author(s):  
J. Plenge ◽  
A. Wirsing ◽  
C. Raschpichler ◽  
M. Meyer ◽  
E. Rühl
Keyword(s):  
Multiphoton Ionization ◽  
Nitrogen Control ◽  
Rotational Excitation ◽  
Chirped Pulse
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