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Description:
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The structures , vibrational frequencies , and potential energy functions of several
molecules in their ground and excited electronic states were determined using various
spectroscopic and theoretical methods .
High -level ab initio and density functional theory (DFT ) calculations were
utilized to investigate the previously reported structures and vibrational spectra of 1 ,3 -
disilacyclobutane (13DSCB ) and its 1 ,1 ,3 ,3 -d4 (13DSCB -d4 ) isotopomer . These
calculations confirmed the finding from earlier microwave work that the CSiC angles of
the 13DSCB ring are unexpectedly larger than the SiCSi angles . The calculated
vibrational spectra using density functional theory agreed well with the experimental
data and showed CH2 modes to have unusually low values . The calculations also
confirmed that the individual molecules in the vapor phase are puckered whereas in the
solid they become planar .
The one -dimensional potential energy surfaces (PESs ) for the ring inversion
vibration of 2 -cyclohexen -1 -one and its 2 ,6 ,6 -d3 isotopomer in its ground and singlet
S1 (π ,π* ) electronic states were determined using ultraviolet cavity ringdown
spectroscopy (CRDS ) . The CRDS data allowed several of the quantum states of the ring
inversion vibration to be determined for both the ground and excited electronic states ,
and the data were fit very well with PESs with high barriers to inversion . The infrared
and Raman spectra and DFT calculations were utilized to complete a vibrational
assignment of 2CHO and 2CHO -d3 . A remarkable agreement was seen between the
experimental and calculated spectra .
The fluorescence excitation spectra (FES ) and the single -vibronic level
fluorescence (SVLF ) spectra of jet -cooled 1 ,4 -dihydronaphthalene (14DHN ) were acquired to determine its ring -puckering potential energy function for the ground and
singlet S1 (π ,π* ) electronic states . Ultraviolet , infrared , and Raman spectra were also
recorded to complement the analysis . The potential energy functions showed that the
molecule is planar in both the ground and S1 (π ,π* ) states . A complete vibrational
assignment was carried out for 14DHN using the infrared and Raman data and aided by
DFT calculations .
The ab intio calculations carried out on 2 -methyl -2 -cyclopenten -1 -one (2MCP )
showed that the molecule can have 3 different conformers . Infrared and Raman spectra
of the liquid -phase molecule were recorded and analyzed to complement the theoretical
calculations . |