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1.
S2(B-X) chemiluminescence, primarily from ν′ = 0 and 1, has been observed in alkali atom—SCl2 reactions. The addition of He or Ar buffer gas to the reaction chamber alters the reaction dynamics, and at certain buffer gas pressures the S2 emission originates exclusively from the ν′ = 6–9 vibrational levels of the B(3Σu?) state. 相似文献
2.
L. A. Koroleva V. K. Matveev A. V. Koroleva Yu. A. Pentin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2018,92(3):488-495
The UV absorption spectrum of methacryloyl fluoride molecule in the gas phase is obtained in the wavenumber range of 32300–35900 cm?1. The resolved vibrational structure of this spectrum consists of 153 absorption bands. The assignment of all bands has been made for the first time. Values ν00trans = 35670.0 сm?1 and ν00cis = 35371.1 cm?1 are determined. The fundamental frequencies for isomers in the S0 and S1 states are found. Several Deslandres Tables (DTs) are constructed for the torsional vibration of the s-trans- and s-cis-isomers of the investigated molecule using the NONIUS program. The origins in these DTs correspond to bands attributed to ν00, and to the fundamental frequencies of each isomer in states S0 and S1. These DTs are used to determine harmonic frequencies ωe, anharmonicity coefficients х11, and the frequencies of torsional vibration 0–v transitions up to high values of vibrational quantum number v for s-trans- and s-cis-isomers in both electronic states. The frequencies of torsional vibrations for the s-trans-isomer and the s-cis-isomer in the S0 state are ν″1 = 80.9 сm?1 and ν″1 = 59.8 сm?1, respectively. The frequencies for the s-trans- isomer and the s-cis-isomer in the S1 state are ν′1 = 134.1 сm?1 and ν′1 = 103.6 cm?1, respectively. 相似文献
3.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1977,33(6-7):689-698
Infrared spectrum of methyl cyanide was recorded in the region from 2235–2320 cm−1 with a working resolution of 0.05 cm−1. The transitions of two parallel type bands ν2 and ν3 + ν4 as well as the associated hot bands are assigned. Since the molecular constants for the ground and ν8 vibrational states are known precisely by microwave study for this molecule, highly accurate molecular constants for the upper vibrational states have been determined from those data by a least-squares procedure. 相似文献
4.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1994,50(8-9):1345-1370
The microwave spectrum of dichlorosilylene in excited vibrational states has been measured in the millimetre- and submillimetre-wave regions. Rotational and centrifugal distortion constants were determined for the ν1, ν2, 2ν2 and ν3 excited states of the Si35Cl2 isotopic species and for the ν2 and 2ν2 states of Si35Cl37Cl. Analysis of the Coriolis resonance between the ν1 and ν3 states of Si35Cl2 yielded values of the D Coriolis interaction constant with F constrained, of two higher-order terms and also an accurate value [5.402338(95) cm−1] of the energy difference between the two excited vibrational states. The rotational constants of Si35Cl2 in the first excited states of the three normal vibrations were combined with those of the ground vibrational state reported in a previous paper [M. Tanimoto et al., J. Chem. Phys. 91, 2102 (1989)] to obtain the equilibrium structure, harmonic and cubic/third-order anharmonic potential constants. 相似文献
5.
《Chemical physics letters》1985,117(6):543-549
The μa R-branch rotational spectra of the ground and first excited states of the three lowest vibrational modes of the H2O…HF heterodimer have been observed in the frequency range 40–80 GHz. Coriolis perturbations between the ground vibrational state (υ = 0) and the first excited state of the out-of-plane bending vibration (υβ(0) = 1) show that for a given J the K−1 = 2 levels of υβ(0) = 1 lie approximately 3 cm−1 above the K−1 = 3 levels of υ = 0. The vibrational separation between these two states is estimated to be 70±3 cm−1. This value is consistent with those determined by other methods and reinforces the conclusion that νβ(0) is governed by a double-minimum potential energy function with the quantitative form previously published. A perturbation is also observed in the first excited state of the hydrogen-bond stretching vibration υσ = 1. This manifests itself as a large, negative centrifugal distortion constant DJK = −8.5 MHz compared with 2 MHz in the other vibrational states. 相似文献
6.
Non-radiative transitions. I. S1 ⇝ S0 internal conversion calculations in benzene and deuterobenzene
《Chemical physics》1986,101(1):67-79
Non-radiative rate calculations for the S1 ⇝ S0 transition are presented. Complete vibrational basis sets are used. A Morse oscillator potential is assumed, for both the ν1 and ν2 vibrations. It is shown that the ν1 potential has a dominant influence on the excess energy behaviour of the rates similar to that of the ν2. The increase of the normalized non-radiative rate curves with excess energy is consistent with experimental results. A comparison is made with the non-radiative rates determined using the local-mode approximation for the CH- and CD-stretch vibrations. 相似文献
7.
Lifetimes of C-2 in rotational levels of the B?2Σ+u:ν′ = 0, ν′ = 1 states have been measured. C-2 was produced from bromoacetylene and rare-gas metastables and the B?2Σ+u—X?2Σ+g transition was laser excited. The lifetimes are constant within a vibrational level, 77 = 8 ns for ν′= 0 and 73 = 7 ns for ν′ = 1. The oscillator strength fνo = 0.044 ± 0.004. 相似文献
8.
Stimulated Raman spectroscopy is used to probe the photoexcitation dynamics of CO2-laser-excited SF6 in a molecular free-expansion jet. Time-dependent depletion of rotational levels in the ground state is observed by monitoring the ν1 Raman spectrum at various delay times after the CO2-laser excitation pulse. Optical Stark shifts are also seen, at short delay times, arising from resonances of the IR laser pulse with ν3 transitions from both ground and ν1 = 1 states. Molecules excited to the ν3 = 1 level are detected by scanning the ν1 + ν3 ? ν3 hot band. A direct determination of the anharmonicity X13 = ?2.910 ± 0.002 cm?1 is thus obtained. 相似文献
9.
Sheng-rui Yu Dao-fu Yuan Wen-tao Chen Ting Xie Si-wen Wang Xue-ming Yang Xing-an Wang 《化学物理学报(中文版)》2016,29(1):135-139
We study the photodissociation dynamics of nitrous oxide using the time-sliced ion velocity imaging technique at three photolysis wavelengths of 134.20, 135.30, and 136.43 nm. The O(1SJ=0)+N2(X1∑g+) product channels were investigated by measuring images of the O(1SJ=0) products. Vibrational states of N2(X1∑g+) products were fully resolved in the images. Product total kinetic energy releases (TKER) and the branching ratios of vibrational states of N2 products were determined. It is found that the most populated vibrational states of N2 products are v=2 and v=3. The angular anisotropy parameters (β values) were also derived. The β values are very close to 2 at low vibrational states of the correlated N2(X1∑g+) products at all three photolysis wavelengths, and gradually decrease to about 1.4 at v=7. This indicates the dissociation is mainly through a parallel transition state to form products at lower vibrational states, and the highly vibrational exited products are from a more bent configuration. This is consistent with the observed shift of the most intense rotational structure in the TKER as the vibrational quantum number increases. 相似文献
10.
Resonance absorption of CO(A1Π → X1Σ+) fourth positive bands was used to excite CO molecules selectively into the ν′ = 0 and ν′ = 1 vibrational levels of the A1Π state. Studies of the fluorescence spectra at different added gas pressures yielded effective cross sections for the vibrational relaxation of A1Π, ν′ = 1 and for the quenching of A1π, ν′ = 0 molecules. Very large cross sections up to gas kinetic were measured for the rare gases He, Ne, Ar, and Kr as well as for the molecular species H2, D2 and N2 相似文献
11.
Spectral simulation was used to analyze the molecular rovibrational bands of D2H and H2D at 5600 Å. These bands were previously measured by the ion beam neutralization method. They were assigned to the electronic 3p2B1 ? 2s2A1 and vibrational (ν - ν″) = (0, 0, 0,-0, 0, 0) transitions. Least squares fits to the experimental line-positions were made to determine the asymmetric rotator constants A, B and C for the 2s2A1 and 3p2B1 ν = 0 states of D2H and H2D, hitherto unknown. Lorentz line-profiles were assumed for the D2H and H2D rotational lines, whose widths are mainly governed by the lifetimes of the lower states. The bands at 5600 Å were simulated and the 2s2A1 state lifetimes were estimated to be σ ≥ 0.5 ± 0.2 ps for D2H and σ ≥ 0.4 ± 0.2 ps for H2D. Vibrational constants of D3 and D2H in the 2s2A1 states are determined from the positions of the 0-0 and 0-1 vibrational bands given in respective experimental spectra previously measured. For the first time the vibrational constants ω1 and ω2 of the 2s2A1 state of H2D were estimated from the positions of the 0-0 and 0-1 band maxima. These vibrational constants are compared with the corresponding vibrational constants of their ions. 相似文献
12.
Absolute vibrational quantum numbers for the SO+ (A2Π—χ2Πr) emission system have been determined by measurement of isotope shifts between S16O+ and S18O+ bands. It has been found that the tentative ν″ values reported previously should be decreased by one vibrational quantum number, The definite molecular constants for the SO+ (A2Π,χ2Πr) states are determined and compared with photoelectron spectroscopic data. 相似文献
13.
《Chemical physics letters》1985,114(4):353-358
Anharmonic potential energy functions for the stretching vibrational motions of the two lowest doublet states of chloro-acetylene cation have been constructed using ab initio RHF SCF calculations and some experimental information. Stretching vibrational frequencies are calculated variationally for four different isotopomers. The ν1 vibrations of H12C235Cl+ are predicted to occur at 3176 (X̃ 2Π) and 3231 (à 2Π) and the ν2 vibration of the à state at 2081 cm−1. 相似文献
14.
A systematic quantum mechanical study of the possible conformations, their relative stabilities, vibrational and electronic
spectra and thermodynamic parameters of methyl-3-methoxy-2-propenoate has been reported for the electronic ground (S0) and first excited (S1) states using time-dependent and time-independent Density Functional Theory (DFT) and RHF methods in extended basis sets.
Detailed studies have been restricted to the E-isomer, which is found to be substantially more stable than the Z-isomer. Four
possible conformers c′Cc, c′Tc, t′Cc, t′Tc, of which the first two are most stable, have been identified in the S0 and S1 states. Electronic excitation to S1 state is accompanied with a reversal in the relative stability of the c′Cc and c′Tc conformers and a substantial reduction
in the rotational barrier between them, as compared with the S0 state. Optimized geometries of these conformers in the S0 and S1 states are being reported. Based on suitably scaled RHF/6-31G** and DFT/6-311G** calculations, assignments have been provided to the fundamental vibrational bands of both these conformers in terms of frequency,
form and intensity of vibrations and potential energy distribution across the symmetry coordinates in the S0 state. A complete interpretation of the electronic spectra of the conformers has been provided. 相似文献
15.
Normal vibrations of ethylbenzene in the first excited state have been studied using resonant two-photon ionization spectroscopy. The band origin of ethylbenzene of S1←S0 transition appeared at 37586 cm-1. A vibrational spectrum of 2000 cm-1 above the band origin in the first excited state has been obtained. Several chain torsions and normal vibrations are obtained in the spectrum. The energies of the first excited state are calculated by the time-dependent density function theory and configuration interaction singles (CIS) methods with various basis sets. The optimized structures and vibrational frequencies of the S0 and S1 states are calculated using Hartree-Fock and CIS methods with 6-311++G(2d,2p) basis set. The calculated geometric structures in the S0 and S1 states are gauche conformations that the symmetric plane of ethyl group is perpendicular to the ring plane. All the observed spectral bands have been successfully assigned with the help of our calculations. 相似文献
16.
Dr. Agnes Perrin Dr. Andrea Flores Antognini Prof. Dr. Xiaoqing Zeng Dr. Helmut Beckers Prof. Dr. Helge Willner Prof. Dr. Guntram Rauhut 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(33):10323-10331
Gas‐phase FTIR spectra of the ν6 (B‐type) and the ν4 (C‐type) fundamental bands of S2N2 (D2h) were recorded with a resolution of ≤0.004 cm?1 and the vibrational spectrum of S2N2 (D2h) in solid Ar has been revisited. All IR‐active fundamentals and four combination bands were assigned in excellent agreement with calculated values from anharmonic VPT2 and VCI theory based on (explicitly correlated) coupled‐cluster surfaces. Accurate experimental vibrational ground‐ and excited‐state rotational constants of 32S214N2 are obtained from a rovibrational analysis of the ν6 and ν4 fundamental bands, and precise zero‐point average rz (Rz(SN)=1.647694(95) Å, αz(NSN)=91.1125(33)°) and semi‐experimental equilibrium structures (Re(SN)=1.64182(33) Å, αe(NSN)=91.0716(93)°) of S2N2 have been established. These are compared to the solid‐state structure of S2N2 and structural properties of related sulfur nitrogen compounds and to results of ab initio structure calculations. 相似文献
17.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1993,49(11):1659-1681
This article is the second part on ℓ-resonance effects on the rotation-vibration bands of acetylene observed in the ν5 fundamental region. While the first part concentrated on the energy level analysis of the fundamental and the seven strongest hotbands originating in the ν4 and ν5 excited states for both major isotopes [Spectrochim. Acta 48A, 1203 (1992)], this article summarizes the results of the analysis of the hotbands 2ν4 + ν5 ← 2ν4, ν4 + 2ν5 ← ν4 + ν5, and 3ν5 ← 2ν5 from which improved molecular constants for the 2ν4 and three quantum energy levels were derived for the major isotope 12C2H2. The mixing levels within the excited vibrational states due to vibrational and rotational ℓ-resonance effects are discussed which lead to the identification of the strong “forbidden” Δℓ3 band, 2ν4+ ν35←2νOe4 as a result of ℓ-resonance intensity perturbation. 相似文献
18.
《Chemical physics》1986,102(3):305-312
In this paper, we report on absolute fluorescence quantum yields from photoselected vibrational states of jet-cooled 1,4-diphenylbutadiene for excess vibrational energies, Ev = 0−7500 cm−1, above the apparent electronic origin of the S1(2Ag) state. The pure radiative lifetimes, τr, of the strongly scrambled S2(1Bu)—S1(2Ag) molecular eigenstates (Ev = 1050−1800 cm−1) show a marked dilution effect, (τr/τr(S2) ≈ 40), being practically identical with the τr values from the S1(2Ag) manifold (Ev = 0–900 cm−1), which is affected by near-resonant vibronic coupling to S2(1Bu) and exhibiting the dynamic manifestations of the intermediate level structure. Isomerization rates in the isolated molecule, which do not exhibit vibrational mode selectivity, were recorded over the energy range 0–6600 cm−1 above the threshold. 相似文献
19.
Martin Quick Marc‐André Kasper Celin Richter Dr. Rainer Mahrwald Dr. Alexander L. Dobryakov Dr. Sergey A. Kovalenko Dr. Nikolaus P. Ernsting 《Chemphyschem》2015,16(18):3824-3835
β‐Carotene in n‐hexane was examined by femtosecond transient absorption and stimulated Raman spectroscopy. Electronic change is separated from vibrational relaxation with the help of band integrals. Overlaid on the decay of S1 excited‐state absorption, a picosecond process is found that is absent when the C9‐methyl group is replaced by ethyl or isopropyl. It is attributed to reorganization on the S1 potential energy surface, involving dihedral angles between C6 and C9. In Raman studies, electronic states S2 or S1 were selected through resonance conditions. We observe a broad vibrational band at 1770 cm?1 in S2 already. With 200 fs it decays and transforms into the well‐known S1 Raman line for an asymmetric C=C stretching mode. Low‐frequency activity (<800 cm?1) in S2 and S1 is also seen. A dependence of solvent lines on solute dynamics implies intermolecular coupling between β‐carotene and nearby n‐hexane molecules. 相似文献
20.
IR-spectra of stable and metastable isomers of ruthenium nitrosocomplexes, [Ru(NO)Cl5]2? and [Ru(NO)(CN)5]2?, have been calculated within the frames of density functional theory. Frequency assignment was refined on the base of analysis of normal vibration in internal vibrational coordinates. Calculation results confirm that spectrally observed metastable states are bond isomers with ν1-ON and ν2-NO coordination. 相似文献