Intensity Of Vibrational Bands Research Articles

Characterization of Dopant Diffusion within Semiconducting Polymer and Small-Molecule Films Using Infrared-Active Vibrational Modes and Attenuated Total Reflectance Infrared Spectroscopy

Understanding dopant diffusion within organic and polymeric semiconductors is of great importance toward the development of organic photovoltaic and electronic devices, many of which require layered structures with controlled doping profiles (e.g., p-n and p-i-n structures). The current paper demonstrates a new method to determine the diffusion and permeability coefficients for dopant diffusion within polymeric and small-molecule organic semiconductors using attenuated total reflectance infrared (ATR-IR) spectroscopy and taking advantage of the intense IR-active vibrational bands created when dopants such as iodine accept charge from a semiconducting polymer to generate polaronic species. The diffusion and permeability coefficients for iodine within poly(3-hexylthiophene) (P3HT) are determined to be 2.5×10(-11)±1.2×10(-11) cm2/s and 2.4×10(-8)±1.2×10(-8) cm2/s·atm, respectively. The approach is applied to P3HT/PCBM (1:1 mass ratio) films, and the diffusion and permeability coefficients through these composite films are determined to be 7.8×10(-11)±2.8×10(-11) cm2/s and 4.8×10(-8)±1.3×10(-8) cm2/s·atm, respectively. Finally, the approach is extended to determining iodine diffusion within the polycrystalline semiconductor tetraphenylporphyrin (TPP) in a bilayer film with P3HT, and the diffusion coefficient of iodine through TPP is determined to be 7.1×10(-14)±1.1×10(-14) cm2/s. Although the current paper determines diffusion and permeability for the dopant iodine, this approach should be applicable to a wide array of dopants and polymeric and small-molecule semiconductors of interest in photovoltaic and electronic applications.

On the carbonaceous carriers of infrared plateau and continuum emission

This study explores the molecular origins of plateaus and continua underlying the infrared and far-infrared (far-IR) bands emitted by compact nebulae, especially protoplanetary nebulae. Computational organic chemistry codes are used to deliver the vibrational integrated band intensities of various large, typical carbonaceous structures. These spectra are composed of a rather continuous distribution of weak modes from which emerge the fingerprints. The 6–18 μm region is interspersed with a great many weak lines, to which the plateaus are assigned. Similarly, the far-IR spectrum is ascribed to the phonon (skeletal) spectrum which is readily identified beyond 18 μm. The absorptivities and absorption cross-sections per interstellar H atom deduced from these spectra are comparable with those of laboratory dust analogues and astronomical measurements, respectively. Moreover, the 5–35 μm spectra of two typical protoplanetary nebulae were reasonably well simulated with combinations of molecules containing functional groups which carry the 21- and 30-μm bands, and molecules devoid of these but carrying strong phonon spectra. These results may help understand the emergence of plateaus, the origin of continua underlying far-IR bands, as well as the composition of circumstellar dust.

A theoretical systematic study of a series of isocyanopolyynes

Several isocyanopolyynes, HCnNC (n=0, 2,…,16), are analyzed in this theoretical work. We performed calculations at MP2/cc-pVTZ (n=0–16), CCSD/cc-pVDZ (n=0–12) and CCSD/cc-pVTZ (n=0–6) levels. The dipole moments from the best treatment, CCSD/cc-pVTZ, are in much closer agreement with those obtained in CCSD/cc-pVDZ calculations (deviations up to 0.05 Debye) than with the results from MP2/cc-pVTZ (discrepancies that can reach 0.55 Debye). Moreover, the CCSD/cc-pVTZ level yields values in excellent accordance with experimental dipole moments for HNC and HC2NC. Hence, this allows concluding that the correct treatment of electron correlation is more important than increments in basis sets for this electric property in isocyanopolyynes and CCSD/cc-pVDZ values are indicated as the best estimates available for large isocyanopolyynes. The findings from infrared intensities of fundamental vibrational bands are also similar (mean deviations of 3.1kmmol−1 for CCSD/cc-pVDZ and 12.6kmmol−1 for MP2/cc-pVTZ with respect to CCSD/cc-pVTZ results). Thus, we decided to use the charge – charge flux – dipole flux (CCFDF) model from multipoles given by the Quantum Theory of Atoms in Molecules (QTAIM), which were obtained at the CCSD/cc-pVDZ level, to investigate the variations in infrared intensities of some selected modes along these systems. The intensity of the band associated with CH stretching shows an increase with the size of these molecules (from 96 to 146kmmol−1 between n=4 and 12) that is readily explained by variations in the charge flux contribution to this mode, in a similar way as found before for cyanopolyynes. Furthermore, the degenerate CH bending vibrations present almost constant intensities in these isocyanopolyynes (around 37–38kmmol−1 from n=4 up to n=12) and this pattern is supported by CCFDF/QTAIM contributions. The band mostly assigned to stretching of the NC triple bond, which can also be described as asymmetric stretching mode of all pairs of adjacent triple bonds, shows an increase of intensity up to n=6 and is associated to values around 96–102kmmol−1 in the remaining larger members. Another important mode detected is a symmetric stretching of NC and CC triple bonds belonging to the isonitrile end (between 66 and 101kmmol−1 when n=6–12) for which the charge contribution is nearly constant and dynamic contributions change in a more complicated way. The most intense fundamental band in each isocyanopolyyne from n=4 to 12 is assigned to vibrations of triple bonds in both ends of these systems (from 129 to 164kmmol−1) and an alternating behavior according with even or odd numbers of CC triple bonds is observed for these values and also for respective CCFDF/QTAIM contributions. Finally, this work also brings values derived from regressions that are indicated as the best estimates of rotational constants and dipole moments to be used for detection of large isocyanopolyynes in the interstellar medium.

Vibrational spectroscopic study of poly(dimethylsiloxane)-ZnO nanocomposites

A series of poly(dimethylsiloxane)-zinc oxide (PDMS-ZnO) nanocomposites having different concentrations of ZnO nanoparticles (0, 1, 5, 10 and 20wt%) have been prepared. Raman and FTIR-ATR spectroscopic analysis was performed in order to determine the interaction between the ZnO nanoparticles and PDMS polymer matrix. Density functional theory (DFT) using the (B3-LYP)/6-311++G(2df,2p) method was used to investigate the vibrational spectra of PDMS. A complete vibrational assignment is supported by the normal coordinate analysis, calculated Raman activities as well as IR intensities.The presence of ZnO nanoparticles in PDMS gives rise to significant differences in relative intensities of the characteristic vibrational bands with respect to the cross-linked polymer. The changes in relative intensities of Raman bands, as well as swelling measurements, were used to explain the effect of ZnO nanoparticles on the cross-linked structure of PDMS nanocomposites. It is established that ZnO nanoparticles influence the cross-linking density of the polymer matrix.

Molecular structure and spectroscopic characterization of ethyl 4-aminobenzoate with experimental techniques and DFT quantum chemical calculations

The FT-IR and FT-Raman spectra of ethyl 4-aminobenzoate (EAB) in the solid phase were recorded. The fundamental vibrational wavenumbers, intensities of vibrational bands and the optimized geometrical parameters of the compound were evaluated using DFT (B3LYP) method with 6-311++G(d,p) basis set. The stable geometry of the compound was determined from the potential energy surface scan. Complete vibrational assignments and Natural Bond Orbital (NBO) analysis for the title compound were carried out. The assignments of the vibrational spectra were carried out with the help of normal co-ordinate analysis (NCA) following the Scaled Quantum Mechanical Force Field (SQMFF) methodology. The molecule orbital contributions were studied by using the total (TDOS), partial (PDOS), and overlap population (OPDOS) density of states. UV–visible spectrum of the compound was recorded and the electronic properties, such as HOMO and LUMO energies were performed by time-dependent DFT (TD-DFT) approach. Mulliken population analysis on atomic charges were also calculated. Besides, molecular electrostatic potential (MEP) and thermodynamic properties were performed.

Spectroscopy-based study on the interaction between gold nanoparticle and poly(vinylpyrrolidone) molecules in a non-hydrocolloid

The study of the interaction between poly(vinylpyrrolidone) (PVP) and gold (Au) nanoparticles (NPs) in a colloid is of special interest for possible applications in the field of catalysis, biosensing, and biomedicine. A strong optical absorption arising from Au NPs at 532 nm in Au-PVP colloids is ascribed to surface plasmon resonance. The X-ray photoelectron spectroscopic results confirm reduction of the Au3+ ion to Au0. A noticeable decrease in the binding energies of the Au4f doublet peak of the Au NP with PVP as compared to the bulk Au atom implies interfacial interaction between the Au NP and PVP molecules. A marked enhancement in vibrational band intensities of C-H (2,961, 2,936, and 2,872 cm−1) stretching, C-N (1,463 cm−1) stretching, and CH2 (1,381 cm−1) bending vibrations in the pyrrolidone ring of PVP molecules reveals a charge-transfer-type interaction between the PVP molecules and surface of the Au NP. A significant decay of the emission band intensity (approximately 85%) in the π ← π* band of the PVP molecules at approximately 392 nm in the presence of Au NPs suggests non-bonding (n) electron transfer from the O atom of the pyrrolidone ring of PVP molecules to the electron-deficient Au NP. A negative zeta potential of (−) 15.2 mV reveals accumulation of n-electrons of the O atom of the carbonyl group of PVP molecules on the surface of the Au NP. Transmission electron microscopic images of PVP-capped Au NPs corroborate the spectroscopic results.

Chemometric discrimination of genetically modified Coffea arabica cultivars using spectroscopic and chromatographic fingerprints

Multivariate statistical design and principal component analysis (PCA) applied to RP-HPLC-DAD and FTIR spectroscopic data were performed to investigate the fingerprints of four coffee cultivars, traditional red bourbon and three genetically modified cultivars. The design and response surface results showed that extraction dependence on solvent composition of one of the genetically modified cultivars, IAPAR 59, was very similar to that found for the red bourbon standard. PCA of the FTIR spectra obtained from all the simplex centroid design mixtures indicated that the 1:1 binary ethanol–dichloromethane solution resulted in the best separation of the four cultivars. The IPR 108 cultivar has more intense vibrational bands in the 3200–3600cm−1 and 1100–1600cm−1 regions indicating higher acid and fat levels than those of the other cultivars. The UV absorptions close to 275nm of the RP-HPLC-DAD spectra are correlated with the strengths of the infrared absorptions between 3400 and 3460cm−1 and can be explained by varying caffeine concentrations in the four cultivars.

Molecular structure, vibrational spectra, first hyperpolarizability and HOMO–LUMO analysis of p-acetylbenzonitrile using quantum chemical calculation

The FT-IR and FT-Raman spectra of p-acetylbenzonitrile (p-ABN) are recorded in the solid phase. The fundamental vibrational frequencies, intensity of vibrational bands and the optimized geometrical parameters of the compound are evaluated using MP2 and DFT (B3PW91) methods with 6-31G basis set. The theoretical frequencies are scaled down and compared with experimental values which showed good agreement. Comparison of the simulated spectra with experimental spectra provides important information about ability of the hybrid computational method to describe the vibrational modes. The investigation of non-linear optical properties, the electric dipole moment μ, polarizability α, anisotropy of polarizability Δα, and molecular first hyperpolarizability β were computed. The linear polarizabilities and first hyperpolarizabilities of the studied molecule indicate that the molecule can be a candidate of non-linear optical material. The HOMO, LUMO, chemical hardness (η), chemical potential (μ), electrophilicity value (ω), total energy, and dipole moment are calculated by MP2 and DFT/B3PW91 using 6-31G basis set. The molecular electrostatic potential (MESP) is also calculated and corresponding graphs are drawn. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond orbital analysis. Finally, some thermodynamic parameters are also calculated and discussed.

Conformational stability, vibrational assignments of 2,3-dihydroxy benzaldehyde as supported by ab initio, hybrid density functional theory and normal coordinate analysis

FT-IR and FT-Raman spectra of 2,3-dihydroxybenzaldehyde (DHB) have been recorded in the regions 4000–400cm−1 and 3500–100cm−1, respectively. The fundamental vibrational frequencies and intensity of vibrational bands were evaluated using density functional theory (DFT) both B3LYP/6-31+G (d, p) and HF/6-31+G (d, p) basis sets combination. There are eight possible conformers (Cn, n=1–8) for this molecule. The computational results identify the most stable conformer of DHB as the C6 form. The molecular structures, vibrational frequencies infrared intensities and Raman scattering activities were calculated. The spectroscopic and theoretical results are compared to the corresponding properties for DHB of C6 conformer. The optimized geometries and normal modes vibration obtained from DFT method are in good agreement with the experimental data. The formation of intermolecular hydrogen bond was investigated using NBO calculations. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule and ESP contour map shows the electrophilic and nucleophilic region of the molecule.

Molecular Structure, NMR, HOMO, LUMO, and Vibrational Analysis of O-Anisic Acid and Anisic Acid Based on DFT Calculations

This work deals with the vibrational spectroscopy of O-Anisic acid (OAA) and Anisic acid (AA). The fundamental vibrational frequencies and intensity of vibrational bands were evaluated using density functional theory (DFT) with standard B3LYP/6-31G** method and basis set combinations. The vibrational spectra were interpreted, with the aid of normal coordinate analysis based on a scaled quantum mechanical force field. The infrared and Raman spectra were also predicted from the calculated intensities. The effects of carbonyl and methyl substitutions on the structure and vibrational frequencies have been investigated. Comparison of simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes. The13C and1H NMR chemical shifts of the DFA and CA molecules were calculated using the gauge-invariant-atomic orbital (GIAO) method in DMSO solution using IEF-PCM model and compared with experimental data.

Confocal Raman spectroscopic analysis of the cytotoxic response to cisplatin in nasopharyngeal carcinoma cells

Apoptosis of nasopharyngeal carcinoma cells (C666 cell line) induced by an anticancer drug cisplatin was investigated by confocal Raman micro-spectroscopy using near-infrared laser (785 nm) excitation in this study. The Raman spectra of C666 cells treated with different concentrations of cisplatin (0.5, 1, 5 and 10 μg mL−1) for 24 h and different treatment times (6, 12, 18 and 24 h) with 5 μg mL−1 cisplatin were collected separately. Difference in the intensities of Raman peaks assigned to the DNA band (783 cm−1, 1338 cm−1, 1523 cm−1 and 1576 cm−1) between the cells treated with cisplatin and control cells becomes greater as the concentration of cisplatin increases, indicating that the cytotoxicity of cisplatin for NPC cells is likely related to its concentration. The major difference between the apoptotic C666 cells incubated with cisplatin and the non-treated cells is the reduction in intensities of vibration bands generated by cellular nucleic acids, proteins and lipids. Large intensity reduction in nucleic vibrations at 783, 1523 and 1576 cm−1 was observed upon apoptosis of the C666 cells. In particular, up to 14.1% and 49.6% reduction in the magnitude of the peaks at 783 cm−1 and 1523 cm−1 respectively in Raman spectra of the apoptotic cells was observed after 24 h of cisplatin treatment, which suggests the breakdown of phosphodiester bonds and DNA bases. Moreover, the intensity of peaks at 1002 and 1447 cm−1 respectively fell to 40.9% and 43.1% of the original value, which indicates that cisplatin could induce apoptosis of C666 cells and reduce the amount of nucleic acid and protein in the cells. These results demonstrate that Raman spectroscopy is a novel, nondestructive mean for studying the anticancer-treated carcinoma cells, which could also provide abundant information about the changes in biochemical properties of cells and serve as an effective method for real time measurement of apoptosis.

Multifunctional rare earth or bismuth oxide materials for catalytic or electrical applications

We present a review on catalytic or electrical properties of materials based on rare earth (RE) oxides (CeO2 ,L a2O3, Lu2O3) or bismuth based composite systems CeO2-Bi2O3, susceptible to be integrated into catalytic microsystems or gas sensors. The polycrystalline solids can be used as catalysts allowing conversion of CO or CH4 traces in air-gas flows. Fourier Transform infrared spectroscopy is used to determine the conversion rate of CO or CH4 into CO2 through the variations versus time and temperature of vibrational band intensities. The time dependent reactivities are interpreted in terms of an adapted Avrami model. In these catalytic analyses the nature of surfaces of polycrystalline solids seems to play a prominent role in catalytic efficiency. Electrical impedance spectroscopy allows analyzing the variation of conductivity of the system CeO2-Bi2O3. In this system, the specific high ionic conduction of a Bi2O3 tetragonal phase might be linked to the high catalytic activity.

Fourier transform infrared spectra and normal mode analysis of drug molecules: Zidovudine

The FTIR spectra of zidovudine molecule have been recorded in the range 4000–400cm−1. The title compound is used as a drug against AIDS or HIV. The molecular structure, fundamental vibrational frequencies and intensities of vibrational bands are evaluated using density functional theory (DFT) using BLYP, B3LYP, B3PW91 and MPW1PW91 methods with 6-31+G(d,p) standard basis set. Comparison of simulated spectra with the experimental spectrum provides important informations and the ability of the computational method to describe the vibrational modes. These calculations have allowed finding most stable conformational structure of AZT. Calculated results of the title compound indicate that the drug molecule has syn orientation. The glycosidic bond in AZT and a minimum-energy structure in which the glycosy torsion angle χ and torsion angle γ values are consistent with those in the conformation of AZT in the AZT5-triphosphate bound to HIV RT is determined.

Molecular orbital studies (hardness, chemical potential, electrophilicity, and first electron excitation), vibrational investigation and theoretical NBO analysis of 2-hydroxy-5-bromobenzaldehyde by density functional method

In this work, the vibrational spectral analysis was carried out using Raman and infrared spectroscopy in the range 4000–400cm−1 and 3500–100cm−1, respectively, for the 2-hydroxy-5-bromobenzaldehyde (HBB). The experimental spectra were recorded in the solid phase. The fundamental vibrational frequencies and intensity of vibrational bands were evaluated using density functional theory (DFT) with the standard B3LYP/6-311G++(d,p) method and basis set. Normal co-ordinate calculations were performed with the DFT force field corrected by a recommended set of scaling factors yielding fairly good agreement between observed and calculated frequencies. Simulation of infrared and Raman spectra utilizing the results of these calculations led to excellent overall agreement with the observed spectral patterns. The complete assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. The optimized geometric parameters (bond lengths and bond angles) were compared with experimental values of related compound. The stability of the molecule arising from hyper conjugative interactions and the charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The directly calculated ionization potential (IP), electron affinity (EA), electronegativity (χ), electrophilicity index (ω), hardness (η), chemical potential (μ), and first electron excitation (τ) are all correlated with the HOMO and LUMO energies with their molecular properties. These show that charge transfer occurs within the molecule. Furthermore, molecular electrostatic potential maps (MESP) of the molecule have been calculated.

Molecular geometry, vibrational spectra, atomic charges, frontier molecular orbital and Fukui function analysis of antiviral drug zidovudine

The solid phase FT-IR and FT-Raman spectra of zidovudine (AZT) were recorded in the regions 4000–400 and 3500–100cm−1, respectively. The optimized geometry, frequency and intensity of the vibrational bands of zidovudine were obtained by the Restricted Hartree–Fock (RHF) density functional theory (DFT) with complete relaxation in the potential energy surface using 6-31G(d,p) basis set. The harmonic vibrational frequencies for zidovudine were calculated and the scaled values have been compared with experimental values of FTIR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The harmonic vibrational wave numbers and intensities of vibrational bands of zidovudine with its cation and anion were calculated and compared with the neutral AZT. The DFT calculated HOMO and LUMO energies shows that charge transfer occurs within the molecule. The electron density-based local reactivity descriptors such as Fukui functions were calculated to explain the chemical selectivity or reactivity site in AZT.

Calculation of the intensities of vibrational hydrogen sulfide transitions for remote sensing of high-temperature media

Integral intensities of vibrational bands are calculated for hydrogen sulfide (H2S) taking into account the Fermi and Darling–Dennison resonances. Components of the dipole moment function in normal coordinates and parameters of the effective vibrational Hamiltonian borrowed from the literature are used as initial data. From several sets of the dipole moment function parameters, we have chosen the set of the parameters computations with which provide the closest agreement with the experimental integral intensities of the H2S bands. As a result, predictive computations of the vibrational band intensities (ΣΔυ i = 2) are carried out at temperatures in the range 600–1500 K.

Infrared spectroscopy analyses of air-CH4 or air-CO gas flows interacting with polycrystalline CeO2, La2O3 and Lu2O3 oxides

A comparative study of reactivity between air-CH4 or air-CO gas flows and CeO2, La2O3 and Lu2O3 rare earth oxides was performed using Fourier transform infrared spectroscopy analyses of CO2 gas resulted from the conversion of CH4 or CO gases. Polycrystalline samples of CeO2, La2O3 and Lu2O3 were first prepared by specific precipitation methods followed by low temperature calcination process. In the case of Lu2O3 oxide, a new specific route was proposed. Crystallite dimensions were determined by X-ray diffraction and transmission electron microscopy analyses. Morphologies were characterized using scanning electron microscopy. Specific surface areas were determined from Brunauer-Emmett-Teller (BET) technique. Using infrared spectroscopy analyses, the conversion rates of CH4 or CO into CO2 were determined from the evolutions of CO2 vibrational band intensities, as a function of time and temperature. It was clearly established that, despite its low specific surface, the Lu2O3 oxide presented the highest capacity of conversion of CH4 or CO into CO2.

Evaluation and differentiation of the Betulaceae birch bark species and their bioactive triterpene content using analytical FT-vibrational spectroscopy and GC-MS

BackgroundAiming to obtain the highest triterpene content in the extraction products, nine bark samples from the forest abundant flora of Apuseni Mountains, Romania were Raman spectroscopically evaluated. Three different natural extracts from Betula pendula Roth birch bark have been obtained and characterized using Fourier transform vibrational spectra.ResultsThis study shows that principal components of the birch tree extract can be rapidly recognized and differentiated based on their vibrational fingerprint band shape and intensity. The vibrational spectroscopy results are supported by the GC-MS data. Based on IR and Raman analysis, one can conclude that all the extracts, independent on the solvent(s) used, revealed dominant betulin species, followed by lupeol.ConclusionsSince Raman measurements could also be performed on fresh plant material, we demonstrated the possibility to apply the present results for the prediction of the highest triterpene content in bark species, for the selection of harvesting time or individual genotypes directly in the field, with appropriate portable Raman equipment.

An adiabatic model for calculating overtone spectra of dimers such as (H 2 O) 2

The near-infrared and visible wavelength spectrum of the water dimer is considered to be the major contributor to the so-called water continuum at these wavelengths. However, theoretical models of this spectrum require the simultaneous treatment of both monomer and dimer excitations. A model for treating this problem is proposed which is based upon a Franck-Condon-like separation between the monomer and dimer vibrational motions. In this model, one of the monomers is treated as the chromophore and its absorption is assumed to be given by its, possibly perturbed, vibrational band intensity. The main computational issue is the treatment of separate monomer and dimer motions. Various approaches for obtaining dimer vibration-rotation tunnelling spectra that allow for monomer motion are explored. These approaches include ways of treating the adiabatic separation of dimer vibrational modes from monomer vibrational modes. We classify the adiabatic separation methods under four main approaches: namely fixed-geometry, free-monomer, perturbed-monomer and coupled-monomer methods. The latter being the most computationally expensive as the monomer wave functions are dependent on the dimer coordinates. For each of these approaches, expectation values over the full potential are calculated for the given monomer vibrational wave functions. Various full (named VAP 2pD in the text) and partial (VAP (+p)D) averaging techniques are outlined to calculate the vibrationally averaged, monomer state-dependent, dimer interaction potentials. The computational costs associated with application of these techniques to the water dimer are estimated and the prospects for full calculations based on this approach are assessed.

What Is the Best DFT Functional for Vibronic Calculations? A Comparison of the Calculated Vibronic Structure of the S1–S0 Transition of Phenylacetylene with Cavity Ringdown Band Intensities

The sensitivity of vibronic calculations to electronic structure methods and basis sets is explored and compared to accurate relative intensities of the vibrational bands of phenylacetylene in the S(1)(A(1)B(2)) ← S(0)(X(1)A(1)) transition. To provide a better measure of vibrational band intensities, the spectrum was recorded by cavity ringdown absorption spectroscopy up to energies of 2000 cm(-1) above the band origin in a slit jet sample. The sample rotational temperature was estimated to be about 30 K, but the vibrational temperature was higher, permitting the assignment of many vibrational hot bands. The vibronic structure of the electronic transition was simulated using a combination of time-dependent density functional theory (TD-DFT) electronic structure codes, Franck-Condon integral calculations, and a second-order vibronic model developed previously [Johnson, P. M.; Xu, H. F.; Sears, T. J. J. Chem. Phys. 2006, 125, 164331]. The density functional theory (DFT) functionals B3LYP, CAM-B3LYP, and LC-BLYP were explored. The long-range-corrected functionals, CAM-B3LYP and LC-BLYP, produced better values for the equilibrium geometry transition moment, but overemphasized the vibronic coupling for some normal modes, while B3LYP provided better-balanced vibronic coupling but a poor equilibrium transition moment. Enlarging the basis set made very little difference. The cavity ringdown measurements show that earlier intensities derived from resonance-enhanced multiphoton ionization (REMPI) spectra have relative intensity errors.