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НазваDissociation of Benzene Molecule in a Strong Laser Field (пошукова робота)
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РозділІноземна мова, реферати англійською, німецькою
ФорматWord Doc
Тип документуРеферат
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Dissociation of Benzene Molecule

 

in a Strong Laser Field

 

 

 

 

 

 

 

1. Introduction.

 

The number of articles devoted to the interaction of molecules with a

strong laser field increased considerably in recent years. The main

features of interaction between diatomic molecules and a laser radiation

were considered in a great number of experimental [1-5] and theoretical

[6-9] papers. Classical and quantum investigations of spatial alignment

of diatomic molecules and their molecular ions in a strong laser field,

as well as ionization and dissociation of these molecules and their

molecular ions account for physical pictures of all processes.

 

However, when considering complex organic molecules, we observe physical

phenomena to be richer, and they are not thoroughly investigated. Most

of results obtained for diatomic molecules can be generalized to the

multi-atomic molecules. This short paper contains the results of

theoretical derivations for dissociation of benzene molecule C6H6 in the

field of linearly polarized Ti:Sapphire laser. Data were taken from

experimental results by Chin’s group, Ref. [4]. We use the atomic system

of units throughout the paper.

 

 

 

 

 

 

 

2. Theoretical approach.

 

Let us consider the benzene molecule C6H6 in the field of Ti:Sapphire

laser with the wavelength =400 nm, pulse length =300 fs and maximum

intensity Imax=21014 W/cm2. According to Ref. [4] first electron is

ejected from this neutral molecule and then the dissociation of

C6H6+-ion occurs.

 

The most probable channel for decay of this ion is the separation into

the equal parts :

 

 

 

 

 

 

 

Of course, there is another channel for decay of C6H6+-ion which

includes the ejection of the second electron and subsequent Coulomb

explosion of the C6H6++-ion. We do not consider the latter process.

 

The channel (1) is seen to be similar to the dissociation of the

hydrogen molecular ion considered in Ref. [2]. Indeed, the model scheme

of energy levels for C6H6+-ion (see Ref. [4]) reminds the model scheme

of energy levels for H2+ [2] containing only two low-lying electronic

levels: 1g (even) and 1u (odd).

 

Therefore we consider the dissociation process of C6H6+-ion

analogously to that for H2+-ion (see Fig. 1). The benzene molecular ion

has the large reduced mass with respect to division into equal parts.

Hence, its wave function is well localized in space (see Fig. 2) and

therefore we can apply classical mechanics for description of the

dissociation process (1). However, the solution of Newton equation with

the effective potential (see below) does not produce any dissociation,

since laser pulse length is too small for such large inertial system. In

addition to, effective potential barrier exists during the whole laser

pulse and tunneling of the molecular fragment is impossible due to its

large mass ( see Fig. 2). Thus, we should solve the dissociation problem

in the frames of quantum mechanics.

 

 

 

 

 

The ground even electronic term of C6H6+-ion is presented here in the

form of the well-known Morse potential with parameters =2k and De=6.2

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