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Microwave radiation
and electron capture in molecular reactions
Akademisk avhandling som med
tillst?nd av Stockholms Universitet framl?gges till offentlig
granskning f?r avl?ggande av filosofie doktorsexamen fredag den 12
September 2003, Kl 10.00 i sal FD5, Fysikum, AlbaNova
universitetscentrum, Roslagstullsbacken 21, Stockholm.
by
Shirzad Kalhori
Doctoral thesis 2003
Molecular Physics Division
Department of Physics
University of Stockholm, Sweden
Abstract
This thesis deals
with four different topics in physics. In the first part, the
design, development and construction of a microwave applicator for
chemically reacting samples is reported. We choose the so-called
re-entrant cavity to achieve a very intense and an almost homogenous
electric field in a gap that of the cavity. The measured quantities
for a 5 ml water sample agreed with the calculated values. In the
second part of this thesis we have tried to theoretically show that
microwaves in the 12.24 cm wavelength region could be absorbed by a
liquid phase reaction. The study shows that the microwave photons
can be absorbed and the photon energy can be transferred to the
motion along the reaction path with the help of a solvent effect. In
this study we used a so-called SN2 reaction CH3Cl + Cl- with water
molecules. We found that water molecules have torsional vibration
eigenfrequencies in this wavelength region. This torsional vibration
can with help of the microwave photon energy push the Cl- along the
reaction path and increase the reaction rate. The third part of this
thesis experimentally shows that an electron captured by an ion lead
to molecular dissociation to neutral atoms (or molecules), and also
to the formation of ion-pair fragments. The branching ratios and the
cross section for dissociative recombination of the poly-atomic
molecular ions C2H3+ and C3H7+ under vibrationally relaxed
conditions, and for H3+ molecular ion under rovibrationally relaxed
condition, to neutral channels and for resonant ion-pair formation
are measured. The experiments were performed at the CRYRING (CRYogenic
ion source RING) ion storage ring facility, at the Manne Siegbahn
Laboratory at Stockholm University. The fourth part is a theoretical
calculation of the cross section with help of wave packet method for
the ion-pair formation of H3+. In this part we studied the H2+ + H-
channel from two possible channels. We used one- and two-dimensional
wave packet calculations, where the symmetry changes from D3h to the
C2v in the case of one-dimensional calculation. The method and the
results are discussed in the thesis.
Stockholm 2003
ISBN 91-7265-717-0
This thesis includes the
following papers:
Paper I
A re-entrant cavity for microwave enhanced chemistry.
Kalhori S., Elander N., Svennebrink J. and Stone-
Elander S.
JMPEE Vol. 38 No: 2, 2003 p. 125
Paper II
Quantum chemical model of an S N2
reaction in a microwave field.
Kalhori S., Minaev B.,
Stone-Elander S. and Elander N.
(2002), J. Phys. Chem. A, 106, 8516.
Paper III
An enhanced cosmic-ray flux towards ? persei
inferred from a laboratory study of the H 3+-e-
recombination rate.
McCall B. J., Huneycutt A. J., Saykally R. J.,
Geballe T. R., Djuric N., Dunn G. H., Semaniak J., Novotny O.,
Al-Khalili A., Ehlerding A., Hellberg F.,
Kalhori S., Neau A., Thomas R., ?sterdahl F. and Larsson M.
(2003), Nature, 422, 500.
Paper IV
Resonant ion-pair formation in electron
collisions with rovibrationallycold H 3+.
Kalhori S.,
Al-Khalili A., Ehlerding A., Hellberg F., Neau A., Thomas R.,
Larsson M., Larson ?., Huneycutt A. J., Djuric N., Dunn G. H.,
Semaniak J., Novotny O., ?sterdahl F. and Orel A. E.
To be submitted to Phys. Rev. A.
Paper V
Dissociative recombination of C 2H3+.
Kalhori S., Viggiano
A. A., Arnold S. T., Rosen S., Semaniak J., Derkatch A. M., afUgglas
M., and Larsson M. (2002), A & A, 391, 1159.
Paper VI
Rates and products of the dissociative
recombination of C 3H7+
in lowenergy electron
collision.
Ehlerding A., Arnold S. T., Viggiano A. A.,
Kalhori S., Semaniak J., Derkatch A.
M., Rosen S., afUgglas M., and Larsson M. (2003), J. Phys Chem A,
107, N0. 13.
Contents
Chapter 1
1.1 Introduction
Chapter 2
2.1 A microwave applicator.
2.2 Design requirements for the applicator.
Chapter 3 Theoretical
methods
3.1 Ab initio methods
3.2 Configuration Interaction method
3.3 Density functional theory
Chapter 4
4.1
SN2
reactions
4.2 Solvent effect and solvated reactions
complexes with their vibrational frequencies.
Chapter 5 Electron captures
process
5.1 Dissociative recombination
5.2 The resonant ion-pair (RIP) process
Chapter 6
6.1 Experiment
6.2 Corrections
6.2.1 Toroidal correction
6.2.2 Space charge correction
6.2.3 Scintillation detector
6.2.4 The ion sources
Chapter 7 Data analysis
7.1 The difficulties of the measurement and
calculation of the cross-section
7.2 Measurement of the cross section
7.3 Branching ratios
Chapter 8 The potential
curves
8.1 Introduction
8.2 Total Hamiltonian
8.3 Diabatic (crossing) states
8.4 Adiabatic (non-crossing) states
Chapter 9
9.1 Preparation of the calculation for the RIP
cross section of H3+
9.2 Direct and indirect coupling between the
states
9.3 Rydberg states
Chapter 10
10.1 Calculation of the ion-pair cross section
using the wave packet method
Chapter 11 Results and
discussion
11.1 A re-entrant cavity for microwave enhanced
chemistry.
11.2 Paper II: Solvent effect and microwave
induced SN2 reaction.
11.3 Papers III and IV: Cross section measurement
in DR, RIP and calculation of ion-pair formation by wave packet
method of H3+.
11.4 Dissociative recombination of hydrocarbon
ions C2H3+ and C3H7+ papers V and VI.
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