I= PHOTOABSORPTION STUDIES OF MOLECULES AT HIGH RESOLUTION
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Title of Thesis
PHOTOABSORPTION STUDIES OF MOLECULES AT HIGH RESOLUTION

Author(s)
Zafar Iqbal
Institute/University/Department Details
Department of Physics/ Quaid-i-Azam University
Session
1995
Subject
Physics
Number of Pages
151
Keywords (Extracted from title, table of contents and abstract of thesis)
photoabsorption, absorption spectrum, ultraviolet absorption, intravalent absorptions, diatomic molecules, molecular spectra

Abstract
(ii) The new high resolution absorption spectrum of BaH and BaD are reported in the region from 3000 A to 3800 A using the same experimental technique as given above. The observation include two new electronic transitions of BaH designated as the 1(2E-X2E at 3725 A and the Vll-X2E at 3694 A. The (0,0) band of both the transitions are observed. In BaD 1(2E-X2E at 3750 A and VllX2E is observed at 3680 A. The (0,0), (1,1), (1,0) and (2,1) bands of the L2llX2E system and (0,0), (1,0) bands of the 1(2E-X2E system have been observed. These transitions are forming a np-complex originating from the 7p atomic state of barium. Vibrational and rotational analysis of these newly observed bands have been carried out and corresponding constants are reported.

(iii) The vapor phase vacuum ultraviolet absorption spectra of methyl iodide and methyl bromide have been studied in the region 1200 A to 1500 A and 1100 A to 1250 A respectively using synchrotron radiation as a background source. Many of the Rydberg and intravalent absorptions of the iodine and bromine electrons in the nonbonding p orbitals have been assigned. The Rydberg series terminating at 2E3/2 and 2E1/2 thresholds are reported for the first time at high resolution. A correlation of the molecular Rydberg series of methyl iodide and methyl bromide to the series in xenon and krypton made possible the assignment of the ns, np and nd series. As a result, the ns, np and nd Rydberg series converging to the 2E3/2 and 2E1/2 levels of methyl iodide and methyl bromide have been considerably extended to higher principal quantum numbers, yielding more accurate values of the corresponding ionization potentials. The auto-ionizing resonances attached to the 2E1/2 threshold which are perturbing line intensities of the resonances to the 2E3/2 threshold have been reported for both the molecules. The autoionizing resonances converging to the 2E3/2 and 2E1/2 limits have been parameterized using the multichannel quantum defect theory based on the phase shifted formalism of Cooke and Cromer. It is demonstrated that the nd Rydberg series attached to the 2E1/2 are predominantly autoionized into the 2E3/2 nlcontinuum. It is observed that the autoionization is more pronounced in the CH3Br as compared to that in CH3I.

Download Full Thesis
15941.33 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
1053.69 KB
2 1 Introduction 1
1970.47 KB
  1.1 Motivations 1
  1.2 Fundamental Theory 3
  1.3 Frank-Condon Principle 7
  1.4 Combination Relations And Evaluation Of Rotational Constants 8
  1.5 Dunham Coefficients 9
  1.6 Electronic States 10
  1.7 Electronic Configuration Of Diatomic Molecules 10
  1.8 Interaction Of Electronic Spin 11
  1.9 Hund's Coupling Cases 11
  1.10 A-Type Doubling 14
  1.11 General Selection Rules For Electronic Transitions 15
  1.12 Autoionization 16
  1.13 Rydberg States And Nl -Complexes 18
3 2 Absorption Spectrum Of LiH Molecule 20
1847.17 KB
  2.1 Experimental 22
  2.2 Appearance Of Bands 25
  2.3 Analysis 26
  2.4 Dissociation Energies 29
  2.5 Conclusion 31
4 3 Molecular Spectra Of BaH And BaD 38
2080.82 KB
  3.1 Experimental 39
  3.2 Description Of The Bands Of BaH 40
  3.3 Vibrational And Rotational Analysis Of BaH 41
  3.4 Rydberg States And Ni-Complexes In BaH 44
  3.5 Isotopic Shift 46
  3.6 Description Of The Bands Of BaD 46
  3.7 Vibrational Analysis 47
  3.8 Rotational Analysis 48
  3.9 Nl -Complex In BaD 50
  3.10 Rotational Constants Of BaD 50
  3.11 Dissociation Energy Of l2n State Of BaH And BaD 51
  3.12 Conclusions 52
5 4 Absorption Spectra Of CH3I And CH3Br Molecules 57
9161.06 KB
  4.1 Introduction 57
  4.2 Experimental 60
  4.3 Molecular Structure Of Alkyl Halides 61
  4.4 Analogies Between CH3I And Rare Gas Xenon Spectrum 62
  4.5 Description Of The CH3I Absorption Spectrum 64
  4.6 Multichannel Quantum Defect Theory (MQDT) 72
  4.7 Application Of MQDT To CH3I 77
  4.8 Photoabsorption Spectrum Of CH3Br 82
  4.9 Experimental 83
  4.10 Analogies Between CH3Br And Rare Gas Krypton Spectrum 84
  4.11 Description Of The CH3Br Absorption Spectrum 86
  4.12 Application Of MQDT To CH3Br 88
  4.13 Conclusions 93