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High-resolution Fourier transform infrared (FTIR) spectroscopy of ethylene isotopologues
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Type
Thesis
Author
Gabona, Marissa Gagarin
Supervisor
Tan, Augustine Tuck Lee
Abstract
In this research work, high resolution Fourier transform infrared (FTIR) spectroscopy was used to investigate the rovibrational structures of ethylene isotopologues: 13C12CH4M, 13C2H4, 12C2D4, 13C2D4 and cis-12C2H2D2. The FTIR spectroscopic technique was applied in the studies of the rotational lines both in the fundamental and combination vibrational bands of the aforementioned molecules. The absorption spectra of the vibrational bands of ethylene isotopologues were measured in the mid-infrared region (400 – 5000 cm-1) with unapodized resolution of 0.0063 cm-1 using Bruker IFS 125HR FTIR spectrometer located at the FTIR laboratory of the National Institute of Education (NIE), Nanyang Technological University in Singapore. Furthermore, an additional absorption spectrum of the ν12 band of 12C2D4 molecule was also measured at a resolution of 0.00096 cm-1 on a Bruker IFS 125HR Michelson Fourier transform spectrophotometer using the THz/far-infrared beamline (beam current of about 200 mA) at the Australian Synchrotron in Victoria, Australia.
In this work using the FTIR spectrometer in NIE, the ν12 fundamental band of the 13C12CH4 molecule was studied in the 1350 – 1510 cm-1 spectral region; the ν12 band of 13C2H4 in the 1360 – 1510 cm-1 region and the ν12 band of the 12C2D4 in the 1020 – 1140 cm-1 region. The spectrum of the ν12 band of 12C2D4 was recorded in the 1000 – 1150 cm-1 region in a separate measurement taken at the Australian Synchrotron. Furthermore, the ν12 band of 13C2D4 was recorded in the 1000 – 1140 cm-1 region and the ν6 band of cis-12C2H2D2 in the 990 – 1100 cm-1 in NIE. The ν7 + ν8 combination band of cis-12C2H2D2 was investigated in the 1525 – 1675 cm-1 region while the ν2 + ν12 band of cis-12C2H2D2 was studied in the 2515 – 2960 cm-1 region. Rovibrational analyses of the bands were carried out for 13C12CH4, 13C2H4, 12C2D4, 13C2D4 and cis-12C2H2D2 using Watson’s A-reduced Hamiltonian in the Ir representation to determine the band center, rotational constants and higher-order centrifugal constants for each band. Both Watson’s A-reduced and S-reduced Hamiltonians in the Ir representation were applied to study the rotational structure of the ν12 band of 12C2D4 measured in the Australian Synchrotron and of the ν12 band of 13C2D4 recorded in NIE. Improved ground state constants were achieved by means of ground state combination differences (GSCDs) using the assigned infrared transitions of 13C12CH4, 13C2H4, 12C2D4 and 13C2D4. For the ν12 band of 12C2D4 measured in the Australian Synchrotron and the ν12 band of the 13C2D4 recorded in NIE, the ground state constants derived from the experimental work using both Watson’s A- and S-reduced Hamiltonian in the Ir representation showed close agreement with those derived from theoretical calculations using the B3LYP/cc-pVTZ, MP2/cc-pVTZ, and CCSD/cc-pVTZ levels of theory. The ground state and upper state (v12=1) constants for the ν12 band of 13C2D4 were derived for the first time from this study. Overall, the ground state and upper state (v12=1) constants derived from the single-state rovibrational analyses on the ν12 bands of 13C12CH4, 13C2H4, and 12C2D4 from this study were more precise than those reported in the literature. For the Coriolis interacting bands ν6/ν4, ν7 + ν8/ν2 and ν2 + ν12 /ν2+2ν10 of cis-12C2H2D2 rovibrational coupling terms were necessarily included in the Watson’s Hamiltonian to fit the perturbed lines accurately and to derive accurate spectroscopic constants for the band being analyzed and the perturbing band.
In this work using the FTIR spectrometer in NIE, the ν12 fundamental band of the 13C12CH4 molecule was studied in the 1350 – 1510 cm-1 spectral region; the ν12 band of 13C2H4 in the 1360 – 1510 cm-1 region and the ν12 band of the 12C2D4 in the 1020 – 1140 cm-1 region. The spectrum of the ν12 band of 12C2D4 was recorded in the 1000 – 1150 cm-1 region in a separate measurement taken at the Australian Synchrotron. Furthermore, the ν12 band of 13C2D4 was recorded in the 1000 – 1140 cm-1 region and the ν6 band of cis-12C2H2D2 in the 990 – 1100 cm-1 in NIE. The ν7 + ν8 combination band of cis-12C2H2D2 was investigated in the 1525 – 1675 cm-1 region while the ν2 + ν12 band of cis-12C2H2D2 was studied in the 2515 – 2960 cm-1 region. Rovibrational analyses of the bands were carried out for 13C12CH4, 13C2H4, 12C2D4, 13C2D4 and cis-12C2H2D2 using Watson’s A-reduced Hamiltonian in the Ir representation to determine the band center, rotational constants and higher-order centrifugal constants for each band. Both Watson’s A-reduced and S-reduced Hamiltonians in the Ir representation were applied to study the rotational structure of the ν12 band of 12C2D4 measured in the Australian Synchrotron and of the ν12 band of 13C2D4 recorded in NIE. Improved ground state constants were achieved by means of ground state combination differences (GSCDs) using the assigned infrared transitions of 13C12CH4, 13C2H4, 12C2D4 and 13C2D4. For the ν12 band of 12C2D4 measured in the Australian Synchrotron and the ν12 band of the 13C2D4 recorded in NIE, the ground state constants derived from the experimental work using both Watson’s A- and S-reduced Hamiltonian in the Ir representation showed close agreement with those derived from theoretical calculations using the B3LYP/cc-pVTZ, MP2/cc-pVTZ, and CCSD/cc-pVTZ levels of theory. The ground state and upper state (v12=1) constants for the ν12 band of 13C2D4 were derived for the first time from this study. Overall, the ground state and upper state (v12=1) constants derived from the single-state rovibrational analyses on the ν12 bands of 13C12CH4, 13C2H4, and 12C2D4 from this study were more precise than those reported in the literature. For the Coriolis interacting bands ν6/ν4, ν7 + ν8/ν2 and ν2 + ν12 /ν2+2ν10 of cis-12C2H2D2 rovibrational coupling terms were necessarily included in the Watson’s Hamiltonian to fit the perturbed lines accurately and to derive accurate spectroscopic constants for the band being analyzed and the perturbing band.
Date Issued
2015
Call Number
QD305.H7 Gab
DOI
QD305.H7 Gab
Date Submitted
2015