Excited State Parameters Research Articles

Ultraviolet resonance Raman scattering of azulene: A test of transform theory

Raman excitation profiles (REPs) from a highly excited state in azulene are presented for several vibrational modes. These include four fundamentals, a combination, and an overtone. Experimental REPs are compared to transform theory predictions which are based on the observable absorption spectrum (ABS) of the resonant electronic state. Though both the REPs and the ABS are multimode in nature, the transform provides a single mode link between the two and allows for extraction of excited state parameters on a mode by mode basis. For several modes, excited state frequencies and Franck–Condon coupling constants are estimated. Observed discrepancies between experiment and transform for other modes raise questions as to the applicability of the ‘‘standard assumptions’’ on which the transform is based to all of the vibrational modes in this electronic state. The strongly enhanced Raman scattering also allows depolarization ratios to be determined for all the azulene symmetric ring vibrations and directly confirms previous symmetry assignments.

Detailed aspects of Raman scattering. Overtone and combination intensities and prescriptions for determining excited-state structure

The time-dependent theory of resonance Raman scattering developed by Heller and co-workers is extended to a more general case which considers simultaneous occurrence of excited-state normal-coordinate displacements, force-constant changes, and Duschinsky rotation upon resonant electronic excitation. General expressions are developed for ground-state scattering intensities (fundamentals, overtones, and combinations) in terms of excited-state structural and force-field parameters. It is shown that all factors contributing to the intensities must be considered if accurate excited-state parameters are to be obtained from experimental data. In particular, additional terms which were not explicitly developed in the earlier treatments can dramatically influence the calculated overtone and combination intensities. The results are applied to the redetermination of the displacement of the Mo-Mo coordinate in the delta-delta* excited state of quadruply bonded Mo/sub 2/(O/sub 2/CR)/sub 4/, and compared to an earlier determination which employed a simplified form of the theory. 14 references, 3 figures.

Internal rotation in the spectrum of acetaldehyde

The geometrical structure of acetaldehyde from the microwave spectrum and torsional transitions from the far infrared spectrum have been fitted with a semirigid model in order to obtain the torsional parameters V″ 3 = 415.0 and V″ 6 = 22.3 cm −1 and the torsional energy levels of the isotopic species CH 3CHO, CH 3CDO, CD 3CHO, and CD 3CDO. These have been used in fitting torsional sequences in the 182-nm system of the electronic spectra of these species to obtain the excited state parameters V′ 3 = 880 and V′ 6 = 77 cm −1. Both the ground and excited state parameters are in good agreement with ab initio predictions.

Vibrational Spectra and Force Constants of Symmetric Tops, XLVII. Rovibrational Spectra of Three Monoisotopic H3GeCl Species in the υ6 Region

Fourier transform spectra of the monoisotopic species H3 70Ge35Cl and H3 74Ge37Cl have been recorded in the υ6 region near 600 cm-1 with a resolution of 0.04 cm-1. Rotational analyses based on ∼ 700 data for each isotopomer have been performed, and the excited state parameters υ6 0, A6, B6, Aζ6, η6J, η6K, D6k and F6 have been determined. The previously reported analysis of υ6 data of H3 74Ge35Cl has been repeated employing improved ground state constants, and a r.m.s. deviation of ~ 4 x 10-3 cm-1 has been achieved for the three different isotopic combinations, which show fully consistent excited state parameters.

Photophysics of cis- and trans-1-(1-indanylidene)indane. Spectroscopic evidence for aggregation of the trans isomer

From the temperature and concentration dependence of UV-vis absorption, fluorescence emission and excitation spectra of both trans- and cis-1-(1-indanylidene)indane it is concluded that at concentrations as low as 10 −4 M, aggregation can occur in solutions of the trans isomer. Since the emission is the superposition of the fluorescence of the monomer and an aggregated species, its spectrum is excitation wavelength dependent. The kinetic parameters of teh excited states derived in the past from experiments with solute concentrations larger than 10 −4 M must therefore be used with discretion. The unexpected formation of aggregates of trans-1-(1-indanylidene)indane is discussed on the basis of thermodynamic considerations.

Information contained in non-linear absorption curves with extrema

For generalized energy level schemes of organic absorbers conditions for extrema in intensity-dependent transmission curves are given. They yield relations between unknown excited state parameters and information on multistep absorptions included in the interaction process. The usefulness is demonstrated at a 3-step absorber (N-propyl-acridone).

276-nm absorption band system of m-dichlorobenzene: Rotational band contour analysis

The 276-nm absorption band system ( 1B 2 ← 1A 1 ) of m-dichlorobenzene was photographed under high resolution. The electronic origin band (0, 0) and a band at (0 + 380) cm −1 were subjected to rotational “band contour” analysis. As a result, it is found that the origin band has a type A band contour and that at (0 + 380) cm −1 exhibits a type B band contour. The band contour analysis also yields an accurate determination of the excited state parameters, viz., A′ = 0.0911 ± 0.0003, B′ = 0.02852 ± 0.00005, and C′ = 0.02175 ± 0.00001 cm −1. A model geometry for the molecule m-DCB in its first excited singlet state has been proposed.

Analysis of resonance cars spectra within the frame of a molecular multimode model

The possibilities to obtain parameters of excited electronic states by coherent anti-Stokes Raman spectroscopy are discussed. For the method of excitation profile analysis the experimental values have to be correctet with respect to absorption of the excitation and Raman radiations. Equivalent parameters can be obtained by an analysis of the line shapes of CARS lines without a corresponding correction.

Vibrational spectra and force constants of symmetric tops: High resolution spectra of monoisotopic H 3SiCl in the 2200-cm −1 region and rovibrational analysis of the ν1 and ν4 fundamentals

The gas phase infrared spectra of monoisotopic H 3Si 35Cl and H 3Si 37Cl have been studied in the ν 1 ν 4 region near 2200 cm −1 with a resolution of 0.012 and 0.04 cm −1, respectively, and rotational fine structure for Δ J = ±1 branches has been resolved. In addition, some information on ν 3 + ν 4 of H 3Si 35Cl near 2750 cm −1 has been obtained. ν 1 and ν 4 are weakly coupled by Coriolis x, y resonance, B Ω 14ζ 14 ∼ 2 × 10 −3 cm −1 , only the upper states K′ = 2, l = 0 and K′ = 1, l = −1 being substantially affected. Local perturbation due to rotational l(±1, ±1)-type resonance with ν 3 + ν 5 +1 + ν 6 +1 and ν 3 + ν 5 +1 + ν 6 −1 is revealed in the Δ K = +1 and −1 branches, respectively. From a fit of the experimental line positions, standard deviations of 1.4 and 3.8 × 10 −3 cm −1, respectively, to a model with five interacting levels conventional excited state parameters and interaction constants have been obtained. In H 3Si 35Cl H 3Si 37Cl the fundamentals are ν 1, 2201.94380(15) 2201.9345(7) and ν 4, 2209.63862(8) 2209.6254(2) cm −1 , respectively. Q branches of the “hot” band ( ν 3 + ν 4) − ν 3 and of ν 4 of the 29Si and 30Si species have been detected.

Assignments of charge-transfer transitions in iron(1,3-diketonate) 3 by means of electrochromism

Electrochromism spectra of iron(1,3-diketonate) 3 in a polyvinyl chloride matrix are presented. Differences in electric dipole moments and polarizabilities between excited states and the ground state are calculated from the electrochromism data. On the basis of the excited-state parameters, two charge-transfer transitions may be assigned; one as a charge-transfer to ligand and the other as a charge-transfer to metal. The electrochromism spectra further indicate that iron(1,3-diketonate) 3 in a polyvinyl chloride matrix has a symmetry lower than D 3.

Analysis of Doppler-limited spectra of the CO stretch fundamental of CD 3OH

Doppler-limited linewidth diode laser spectra of the low- J P and R branches of the ν 4 band (CO stretch) of CD 3OH were recorded and analyzed. Hindered internal rotation and molecular asymmetry are handled by exact matrix diagonalization. Fermi resonance between ν 4 and the τ = 1, n = 3 and n = 4 torsional levels of the ground vibration state was found to be responsible for several anomalous spectral features. Direct LMS fitting of the data to a set of 11 excited-state parameters lead to the assignment of 160 lines with a rms error of ±0.00088 cm −1.

Magnetic Resonance on Localized Excited Triplet States in 1,4-Dibromonaphthalene

Abstract Kinetic parameters of localized excited triplet states in 1,4-dibromonaphthalene have been determined from ODMR and MIDP experiments. The results show that no Boltzmann equilibrium exists over the triplet exciton sublevels at the moment of trapping. These experiments are in agreement with our previously reported findings, that in 1,4-dibromonaphthalene excitons exist with a very short lifetime.

Luminescence characteristics of adenosine and its phosphates

Singlet and triplet excited state parameters of adenine, adenosine and adenosine phosphates are determined and compared. Progressive substitution of undissociated terminal phosphate groups increases triplet lifetimes in the order π p (adenosine 5′-triphosphate) > π p (adenosine 5′-diphosphate) > π p((adenosine 5′-monophosphate) > π p (adeninine) > π p (adenine).

Correction. Determination of Geometrical Parameters of Excited States, Application to d6 Transition Metal Complexes of O and D4 Symmetry.

Correction. Determination of Geometrical Parameters of Excited States, Application to d⁶ Transition Metal Complexes of O and D₄ Symmetry.

Confidence in fluorescence lifetime determinations: a ratio correction for the photomultiplier time response with wavelength

The photomultipliers used in single photon counting fluorescence lifetime Systems have a time response function which varies with wavelength. This variation results in a reduced confidence in the kinetic parameters obtained after deconvolution of the lamp intensity decay profile measured at the excitation wavelength from the sample emission decay profile measured at the emission wavelength. Moreover in the case of multi-component decays, inaccurate kinetic parameters are calculated because of this PMT variation. Using weighted residual plots, we demonstrate how one may make a satisfactory subjective appraisal of the adequacy of the deconvolution and the physical model of the decay processes. We have developed a ratio correction technique which accounts for the PMT time response variation with wavelength. This technique requires no apriori assumption of the nature of the PMT effect. Only when the data are corrected using the ratio correction technique can sufficient confidence in the accuracy of the singlet excited state parameters and the validity of the physical model be obtained.

Determination of geometrical parameters of excited states. Application to d6 transition metal complexes of O and D4 symmetry

Determination of geometrical parameters of excited states. Application to d6 transition metal complexes of O and D4 symmetry

The Calorimetric Detection of Excited States.

Calorimetric techniques offer the photophysicist and photochemist the opportunity to measure a number of parameters of excited states which may be difficult to obtain by other techniques. The calorimetric strategy seeks to measure the heating of a sample resulting from radiationless decays or chemical reactions of excited states. Heating is best measured through volume and pressure transducers, and four calorimeters based on these are described. With calorimetric instrumentation one can perform measurements on samples in the gas, liquid and solid phases over a wide temperature range. Moreover time dependent processes with time constants ranging from microseconds to seconds are amenable to study. Examples of the application of calorimetric techniques to the determination of quantum yields of fluorescence, triplet formation and photochemistry are given.

Elastic and inelastic scattering of 12.0-MeV protons fromKr84,86

Differential cross sections for elastic and inelastic scattering of 12.0-MeV protons from $^{84}\mathrm{Kr}$ and $^{86}\mathrm{Kr}$ have been measured. Optical-model parameters obtained from the elastic cross sections were used in distorted-wave-Born-approximation and coupled-channel calculations in order to determine the spin, parities, and deformation parameters of excited states. The deformation parameters found are ${\ensuremath{\beta}}_{2}=0.128 \mathrm{and} 0.108$ for the first ${2}^{+}$ states in $^{84}\mathrm{Kr}$ and $^{86}\mathrm{Kr}$, respectively, and are ${\ensuremath{\beta}}_{3}=0.158 \mathrm{and} 0.145$, respectively, for the first ${3}^{\ensuremath{-}}$ states. Most of the scattering strength to the "two-phonon" states proceed through their one-phonon components. The spins of several higher excited states are suggested.NUCLEAR REACTIONS $^{84,86}\mathrm{Kr}(p,{p}^{\ensuremath{'}})$, $E=12.0$ MeV; measured $\ensuremath{\sigma}(\ensuremath{\theta})$ and level energies; deduced optical-model parameters, ${J}^{\ensuremath{\pi}}$ and $\ensuremath{\beta}$ from DWBA and coupled channels.

Quadrupole fine structure in MODR spectroscopy and the determination of the absolute signs of the ZF parameters of excited triplet states. MODR spectrum of the 3A′ state of 1-bromonaphthalene in durene

We report measurements of the complete orientational dependence of the 3 cm microwave-optical double resonance (MODR) spectrum of the lowest 3(π,π*) state of 1-bromonaphthalene (1BN) in a durene host crystal at liquid helium temperatures. An analysis of the high-field spin Hamiltonian of triplet states containing quadrupolar nuclei shows that both the absolute signs and magnitudes of each of the zero-field (ZF) parameters as well as the principal values of the g, quadrupole, and hyperfine tensors can be determined using MODR techniques. For 3A′ 1BN, we find X/hc = +0.0434 cm−1, Y/hc = +0.0229 cm−1, Z/hc = −0.0663 cm−1, gxx = 2.003, gyy = 2.002, and gzz = 1.994. A comparison of these values with those obtained for 3B2u naphthalene suggests that the ZF scheme of the lowest triplet state of 1BN is modified by spin-orbit coupling with higher excited states, principally in the triplet manifold.

The [formula omitted] transition of formic acid

New sharp bands of formic acid have been observed in the near ultraviolet at the long wave-length end of the previously observed diffuse band system (2250–2500 Å) by considerably extending the absorption path length. Both the diffuse and sharp bands belong to the same vibrational system which is assigned to the π ∗ ← n electronic transition in the carbonyl group. Extensive progressions are observed in the carbonyl stretching frequency which is greatly reduced in the excited state (fundamental ν 3′ ≈ 1080 cm −1) and many intervals of about 400 cm −1 are assigned to the OCO bending frequency ν 7′. A band contour analysis of the 2593 Å band shows that the molecule is nonplanar in the excited state because of the magnitude and sign of the inertial defect. From this analysis, the rotational constants for the excited state are S ‘=1.8755, B ‘0.4042, C ‘=0.3378 cm −1 By the plausible assumption that the important changes in the molecule are in the C=0 bond length, the OCO angle, and the nonplanarity due to the formyl hydrogen, the following excited state parameters are derived. rC=0 = 1.407 A.The changes in formic acid are closely analogous to the changes in formyl fluoride as a result of the π ∗ ← n transition.