Vibronic Emission Spectra Research Articles

Vibronic Emission Spectra of Dithiophene and Terthiophene and Their Complexes with H2S and (H2S)2

In this work, the vibronic emission spectra of dithiophene (T2) and terthiophene (T3) molecules and their complexes with hydrogen sulfide and its dimmer were calculated at the TD-DFT / CAM-B3LYP / 6-31G(d) theory level. The solvent was taken into account within the PCM model. Vibronic spectra were calculated considering both the Herzberg-Teller and Duschinsky effects. Good agreement between the computed and experimental spectra was obtained. The vibration promoting modes forming vibronic progressions were found. Vibronic bands for bithiophene and terthiophene were formed by their low-frequency modes (≤370 cm–1), combinations of low-frequency modes with high-frequency modes (1497 and 1672 cm–1 for T2 and 1516 and 1573 cm–1 for T3), and with their composite high-frequency modes. The intensities of vibronic lines for the emission spectra of T2∙∙∙H2S, T3∙∙∙H2S and T2∙∙∙(H2S)2, T3∙∙∙(H2S)2 complexes were shown to decrease 3.7, 2.6 and 5.5, 3.6 times compared to T2 and T3, respectively. The bathochromic shifts of the vibronic bands of dithiophene and terthiophene complexes with H2S and (H2S)2 did not exceed 130 cm–1 for all bands.

Spectroscopic detection of the stannylidene (H2C=Sn and D2C=Sn) molecule in the gas phase.

The H2CSn and D2CSn molecules have been detected for the first time by laser-induced fluorescence (LIF) and emission spectroscopic techniques through the B̃1B2-X̃1A1 electronic transition in the 425-400nm region. These reactive species were prepared in a pulsed electric discharge jet using (CH3)4Sn or (CD3)4Sn diluted in high-pressure argon. Transitions to the electronic excited state of the jet-cooled molecules were probed with LIF, and the ground state and low-lying Ã1A2 state energy levels were measured from single vibronic level emission spectra. We supported the experimental studies by a variety of ab initio calculations that predicted the energies, geometries, and vibrational frequencies of the ground and lower excited electronic states. The spectroscopy of stannylidene (H2CSn) is in many aspects similar to that of silylidene (H2CSi) and germylidene (H2CGe).

Barely fluorescent molecules. I. Twin-discharge jet laser-induced fluorescence spectroscopy of HSnCl and DSnCl.

The divalent tin transient molecules HSnCl and DSnCl have been detected for the first time by laser-induced fluorescence (LIF) spectroscopy. HSnCl/DSnCl were produced in a twin-discharge jet using separate precursor streams of SnH4/SnD4 and the discharge products from HCl/DCl, both diluted in high pressure argon. The Ã1A″-X̃1A' spectrum of HSnCl consists of a single vibronic 00 0 band with a very short fluorescence lifetime (∼30ns). In contrast, the LIF spectrum of DSnCl exhibits three bands (00 0,20 1,and20 2), whose fluorescence lifetimes decrease from 393ns (00) to less than 10ns (22). Single vibronic level emission spectra have been recorded, providing information on all three vibrational modes in the ground state. Previous detailed ab initio studies indicate that these molecules dissociate into SnCl + H on the excited state potential surface and this is the cause of the short fluorescence lifetimes and breaking off of the fluorescence. It is fortunate that the HSnCl excited state zero-point level is still fluorescent or it would not be detectable by LIF spectroscopy.

Barely fluorescent molecules. II. Twin-discharge jet laser-induced fluorescence spectroscopy of HSnBr and DSnBr.

HSnBr and DSnBr have been detected for the first time by a combination of laser-induced fluorescence (LIF), fluorescence hole-burning, and wavelength resolved emission spectroscopies. The transient molecules were produced in a twin-discharge jet using separate precursor streams of SnH4/SnD4 and HBr/DBr, both diluted in high pressure argon. The Ã1A″-X̃1A' spectrum of HSnBr only consists of the 00 0 and 20 1 cold bands that show clearly resolved subband structure with fluorescence lifetimes varying from 526 to 162ns. The DSnBr LIF spectrum exhibits four bands (00 0, 20 1, 20 2, and 10 1) whose fluorescence lifetimes decrease from 525ns (00) to 175ns (11). Single vibronic level emission spectra have provided extensive information on the ground state vibrations, including all the anharmonicities and the harmonic frequencies. Fluorescence hole-burning experiments have shown that a few higher HSnBr nonfluorescent levels are very short-lived but still detectable. The ab initio studies of Tarroni and Clouthier [J. Chem. Phys. 156, 064304 (2022)] show that these molecules dissociate into SnBr + H on the excited state potential surface and this is the cause of the short fluorescence lifetimes and breaking off of the LIF spectra. HSnBr is a barely fluorescent molecule in the sense that only vibrational levels less than or equal to 317cm-1 in the excited state emit detectable photons down to the ground state.

Coumarin 314 excitation in aqueous media: Contributions of vibronic coupling and hydration

Vibronic coupling and hydrogen bonding were considered when analyzing the excitation of coumarin C314. It was found that the B3PW91 functional in combination with the 6–31++G(d,p) basis set and the IEFPCM solvent model gives a calculated vibronic absorption spectrum, which is in good agreement with the experimental one both in the position of the maximum and in shape. Significant differences are shown between the results of calculating the transition energies using the models of vertical and vibronic transitions. Both a single C314 molecule and its five different hydration complexes with strongly bound water molecules have been analyzed. It was taken into account that a water molecule can attach both to the nitrogen atom N1 (“A” type) and the C=O carbonyl groups of the dye (“B” type). The vibronic emission spectra of a single C314 molecule and its hydrate complexes were also calculated and analyzed.

Observation of vibronic emission spectrum of jet-cooled 3-chloro-4-fluorobenzyl radical

We observed the vibronic emission spectrum of 3-chloro-4-fluorobenzyl radical using a corona-excited supersonic jet expansion (CESE) from the precursor 3-chloro-4-fluorotoluene. From an analysis of the observed spectrum, we investigate the formation of the 3-chloro-4-fluorobenzyl and 4-fluorobenzyl radicals and explained the reaction paths with an ab initio study. The D1 → D0 transition energy and the frequencies of vibrational mode of the 3-chloro-4-fluorobenzyl radical were determined with a Franck-Condon simulation from density functional theory calculations in the D0 and D1 states.

Identification of the Jahn-Teller active trichlorosiloxy (SiCl3O) free radical in the gas phase.

The Ã2A1-X̃2E electronic transition of the jet-cooled trichlorosiloxy (SiCl3O) free radical has been observed for the first time in the 650-590 nm region by laser induced fluorescence (LIF) detection. The radical was produced by a pulsed electric discharge through a mixture of silicon tetrachloride and oxygen in high pressure argon at the exit of a pulsed molecular beam valve. The LIF spectrum shows low frequency intervals, which we assign as activity in the normally forbidden degenerate v5 ' and v6 ' modes, indicative of a significant Jahn-Teller effect in the ground state. Single vibronic level emission spectra show level dependent spin-orbit splittings in the ground state and Jahn-Teller predictable variations depending on which upper state level is pumped. The measured lower state energy levels have been fitted to a Jahn-Teller model that simultaneously includes spin-orbit coupling and linear and quadratic multimode coupling. In SiCl3O, the Jahn-Teller interaction predominates over spin-orbit effects.

Determination of the isotopic composition of enriched materials using laser ablation molecular isotopic spectrometry: partial least squares and multivariate curve resolution for the determination of 15N content in enriched urea.

A quantitative analytical method based on laser ablation molecular isotopic spectrometry (LAMIS) and multivariate analysis was developed and evaluated for the determination of the isotopic composition of enriched materials. The method consists preparing a concentrated solution of the enriched material, using small quantities of a sample (125mg), and ensuring the economic efficiency of the analysis. Standard solutions of known isotopic contents are prepared by employing mixtures of urea highly enriched in 15N and urea of natural isotopic ratio and analyzed by mass spectrometry. A small volume (30μL) of these solutions is delivered to a filter paper disc (3cm diameter). After drying, the disc, offering a homogeneously distributed analyte, is presented to a LAMIS equipment to acquire the vibronic emission spectra containing information about the isotopologues of interest. To illustrate the proposed method, the content of 15N is determined in enriched samples of urea. In this case, each spectrum is normalized by the intensity of emission of the CN isotopologues for the electronic (Δν = 0) emission band at 387.1nm, ensuring better accuracy. Selected regions and single wavelengths of the vibronic emission spectrum (Δν = + 1 or - 1) related to CN species were employed to construct multivariate partial least squares (PLS) and univariate regression models to predict the isotopic content of new samples. Besides, the LAMIS data set was evaluated by multivariate curve resolution (MCR) algorithm. The best MCR and PLS models presented similar results regarding the accuracy to determine 15N content in enriched urea. MCR is capable of identifying spectral interferences and minimizing its effect. The results show that the proposed method based on LAMIS and PLS or MCR multivariate analysis can determine the 15N content in the range 5-50% with a root mean square error of prediction (RMSEP) respectively equal to 0.5 or 0.7% (m/m) in comparison with reference results obtained by mass spectrometry. Graphical abstract.

Chromophor Inhomogeneity Indication by Diffuse Vibronic Spectra

Determination of gap between optically combining states (0-0- transition) from diffuse vibronic absorption or emission spectra is possible now for homogeneous ensembles of chromophores. If the observed spectra present composite polymorphic chromophores or different species they are formed by partial spectra and differing electronic transitions. For these conditions the indicating pure-electronic transition frequency attribute is distorted, smeared or even absent. That behavior is qualitative indication of the chromophore inhomogeneity. The same would be because of impurities. It is shown that the approach of inhomogeneity qualitative indication by spectra is adaptable to different structural forms of chromophor and at polymorphic sites of containing the chromophore media. The experimental data show that the approach is applicable to see the chromophore inhomogeneity by linear and circular vibronic spectra even of molecular dye-labels. The examples of observed distortions for the spectra of different composite species in different media as manifestation of their inhomogeneity are given. As the region of indication 0-0-transition is situated at low intensity antistokes wings of spectra the sensitivity to inhomogeneity is high as to hindrance by impurities and measurement precision.

Heart Rate Recovery and Cardiovascular Risk Factors among Firefighters

We report the vibronic emission spectrum of 4-chloro-m-xylyl radical using a long-path monochromator in a corona-excited supersonic expansion (CESE). By the precursor 4-chloro-m-xylene, we identified 4-chloro-m-xylyl from the two isomeric benzyl-type radicals analyzing a Franck-Condon simulation and ab initio calculations. From an analysis of the vibronic emission spectrum of the 4-chloro-m-xylyl radical, the D1 → D0 electronic transition energy was confirmed and the assignments of vibrational frequencies were accomplished in the ground state.

Generating Function Approach to Single Vibronic Level Fluorescence Spectra.

An efficient time-dependent generating function method to compute vibronic emission and absorption spectra arising from transitions from a singly excited vibrational initial state is presented. In contrast to existing finite temperature approaches that intrinsically contain these transitions weighted by a Boltzmann factor, the current approach allows one to calculate these transitions individually. Using vibrational frequencies and normal modes computed by the second-order approximate coupled cluster (CC2) method, this formalism is used to compute the single vibronic level (SVL) fluorescence spectra of anthracene. Calculated spectra are in excellent agreement with spectra measured in jet-cooled expansion experiments. Duschinsky mixing is necessary to explain intensities of certain peaks. In a few cases, CC2, however, underestimates Duschinsky mixing, leading to too low peak intensities. An empirical correction of the Duschinsky matrix is presented. The presented method has the potential to facilitate the assignment and interpretation of SVL fluorescence spectra.

Observation of vibronic emission spectrum of jet-cooled 4-chloro-m-xylyl radical

We report the vibronic emission spectrum of 4-chloro-m-xylyl radical using a long-path monochromator in a corona-excited supersonic expansion (CESE). By the precursor 4-chloro-m-xylene, we identified 4-chloro-m-xylyl from the two isomeric benzyl-type radicals analyzing a Franck-Condon simulation and ab initio calculations. From an analysis of the vibronic emission spectrum of the 4-chloro-m-xylyl radical, the D1 → D0 electronic transition energy was confirmed and the assignments of vibrational frequencies were accomplished in the ground state.

The blue vibronically resolved electroluminescence of azatrioxa[8]circulene

Organic Light Emitting Dioides (OLED)devices were fabricated with blue emission based on azatrioxa[8]circulene and 4,4-N,N′-Dicarbazolyl-1,1′-biphenyl (CBP) with maximum brightness of 840 kd/m2 at 12 V and the starting voltage of 3.5 V. The vibronic emission spectrum was analyzed by the promotive modes calculation method. The electroluminescence of fabricated OLED device is caused by the 0-0 electronic transition and single excitations of 1473 cm−1 and 1673 cm−1 modes and combinations thereof.

Electronic transition and cascading decay of CuO molecule in the wavelength region 430–550 nm investigated by laser-induced fluorescence spectroscopy

The electronic spectrum of the copper monoxide molecule (CuO) was investigated in the range of 430–550 nm using laser induced fluorescence spectroscopy and single vibronic level emission spectra. The CuO molecule was produced by a supersonic jet-cooled discharge assisted laser ablation of Cu target. Twenty two vibronic bands were observed and assigned to the electronic transition progressions from the ground state X2Пi to excited states C2П3/2, C2П1/2, D2Δ5/2, E2Δ5/2, F2П3/2, G2Σ−, H2П3/2, and I2П3/2, of which ten bands were recorded firstly. The molecular constants of the excited electronic states for 63CuO and 65CuO isotopologues were obtained by a rotational analysis of the spectra. Cascading processes in the electronic excited states were found combining the time-resolved single vibronic level emission spectroscopy. The time-dependent radiative decay curves corresponding to different decay processes were recorded and analyzed.

The high-resolution LIF spectrum of the SiCCl free radical: Probing the silicon-carbon triple bond

A rotationally resolved spectrum of a band of the A∼2Σ+ − X∼2Π electronic transition of the SiCCl free radical has been obtained for the first time. The radical was produced in an electric discharge jet using 1,1-dichlorosilacyclobutane vapor in high pressure argon as the precursor. The laser-induced fluorescence spectrum of the band system in the 610–550 nm region was recorded and the 2Π3/2 spin component of the 0–0 band was studied at high resolution. Rotational analysis gave the B values for the combining states and by fixing the CCl bond lengths at ab initio values we obtained r″ (SiC) = 1.692(1) Å and r' (SiC) = 1.594(1) Å. The bond lengths correspond to a silicon-carbon double bond in the ground state and an unusual SiC triple bond in the excited state. Single vibronic level emission spectra yielded the ground state bending and stretching energy levels up to energies near 5000 cm−1. These were satisfactorily fitted to a Renner-Teller model that included spin–orbit and vibrational anharmonicity effects.

Jet-cooled spectroscopy of the m-ethylbenzyl radical in a corona-excited supersonic expansion.

The vibronic structure of m-ethylbenzyl radical has been investigated in the gas phase for the first time in a corona-excited supersonic expansion (CESE). Assignment of the m-ethylbenzyl radical has been reported by comparing the spectra from m-xylene and m-ethyltoluene. The theoretical calculation, Density functional theory, of the D0 and D1 state structures of the m-ethylbenzyl radical was computed. Conclusive assignment of vibronic emission spectrum has been analyzed with an aid of Franck-Condon simulation in the D0-D1 transition.

The laser-induced fluorescence spectroscopy of gold monoxide: B2Σ−－X2Π3/2 transition

The electronic spectrum of the gaseous gold monoxide molecule has been investigated in the range of 16000－18500 cm−1 using laser induced fluorescence spectroscopy and single vibronic level emission spectra. Five rotationally resolved vibronic bands are observed and assigned to the transitions B2Σ− (v' = 0－4) －X2п3/2 (v'' = 0), in which the 0－0 transition is observed for the first time. The molecular constants of the excited state B2Σ− are obtained by a rotational analysis of the spectra. The spin-orbit coupling constant and the vibrational constants of the ground state X2пi are determined with the accuracy improved by one order of magnitude. The lifetimes of most observed bands are also measured for the first time.

Jet-cooled spectroscopy of the isomeric chloro-p-xylyl radicals in a corona-excited supersonic expansion

We report the jet-cooled isomeric chloro-p-xylyl radicals in a corona-excited supersonic expansion (CESE), and its vibronic spectrum was recorded with a long-path monochromator. By the precursor 2-chloro-p-xylene, we identified the two isomeric benzyl-type radicals, 2-chloro-p-xylyl and 3-chloro-p-xylyl radicals in the corona discharge. The vibronic emission spectrum of the chloro-p-xylyl radicals corresponded to the D1 → D0 electronic transition and determined the electronic transition energy depending on the constitutional isomers.

Visible emission spectroscopy of jet-cooled chloro-substituted 2-methylbenzyl radicals

Four isomeric chloro-substituted 2-methylbenzyl radicals were generated from the corona discharge of 3- and 4-chloro-o-xylenes seeded in a large amount of He carrier gas using a technique of corona excited supersonic expansion coupled with a pinhole-type glass nozzle. The observed visible vibronic emission spectra were analyzed to identify the radical species produced in the discharge, from which the production of the 3-, 4-, 5-, and 6-chloro-2- methylbenzyl radicals was confirmed. In addition, we determined the D1 → D0 electronic transition energies and vibrational mode frequencies in the D0 state of the isomeric chloro-substituted 2-methylbenzyl radicals.

Spectroscopic identification of jet-cooled o-ethynylbenzyl radical generated in corona discharge

The vibronically excited but jet-cooled o-ethynylbenzyl radical was generated from precursor, o-ethynyltoluene seeded in a large amount of carrier gas helium using a home-made pinhole-type glass nozzle combined with the technique of corona excited supersonic expansion. The visible vibronic emission spectrum was recorded with a long-path monochromator from the corona discharge of the precursor. By analyzing the observed spectrum, we determined the electronic energy in the D1 → D0 transition and vibrational mode frequencies in the D0 electronic state of the o-ethynylbenzyl radical.