Lifetimes Of Vibrational States Research Articles

Decaying and revival dynamics of molecules revealed by attosecond wave-mixing spectroscopy.

We theoretically investigate the decaying dynamics in model molecules by using attosecond wave-mixing spectroscopy. We find that transient wave-mixing signal in molecular systems can be used to measure the lifetimes of vibrational states with attosecond time resolution. Typically, there are many vibrational states in the molecular system, and the molecular wave-mixing signal with a specific energy at a specific emitting angle is contributed by many possible wave-mixing pathways. In addition, the vibrational revival phenomenon in the previous ion detection experiments has also been observed in this all-optical approach. This work provides a new, to the best of our knowledge, route for the decaying dynamics detection and wave packet control of molecular systems.

Non-Relativistic Electronic-Structure Computation of Neutral and Cationic Systems [Fr2, Fr-AEM+ (AEM= Ca, Sr, Ba)

The experimental field of ultracold ion-atom mixtures including an alkali-metal atom and an alkaline-earth-metal ion as well as of homonuclear alkali dimers has paved the way for creating and manipulating the ultracold molecules. The present paper is focused on a study of molecules such us francium dimer and a comparative spectroscopic investigation of the cationic systems Fr-(Ca+, Sr+, Ba+). We adopt a computational scheme without spin-orbit coupling reposed on the full configuration interaction and semi-empirical pseudo-potential theory of the atomic cores Fr+, Ca2+, Sr2+, and Ba2+ with extended and optimized basis sets. We have determined the adiabatic potentials with their relative spectroscopic constants, the electric dipole moments and the vibrational levels spacings for the 1,3Σu,g+ and 1,3Σ+ electronic states for Fr2 and Fr-AEM+, respectively, correlated toward {Fr(7s) + Fr(7s, 7p, 6d, 8s, 8p)}, {Ca(4s2, 4s4p, 4s3d), Sr(5s2, 5s5p, 5s4d), Ba(6s2, 6s6p, 6s5d) + Fr+}, and {Ca+(4s, 3d), Sr+(5s, 4d), Ba+(6s, 5d) + Fr(7s, 7p)}. The accuracy and reliability of the current results are discussed by comparing with theoretical data available in the literature. The occurrence of some avoided crossings between the neighboring electronic states is leading to a charge or excitation transfer for atom-ion collisions in the diverse charge or excited states. The Σ+-Σ+ transitions are determined in order to evaluate the future radiative lifetimes of vibrational states serving the direct laser cooling.

Ab initio electronic structure and prospects for the formation of ultracold calcium–alkali-metal-atom molecular ions

Experiments with cold ion–atom mixtures have recently opened the way for the production and application of ultracold molecular ions. Here, in a comparative study, we theoretically investigate ground and several excited electronic states and prospects for the formation of molecular ions composed of a calcium ion and an alkali-metal atom: CaAlk+ (Alk = Li, Na, K, Rb, Cs). We use a quantum chemistry approach based on non-empirical pseudopotentials, operatorial core-valence correlation, large Gaussian basis sets, and full configuration interaction method for valence electrons. Adiabatic potential energy curves, spectroscopic constants, and transition and permanent electric dipole moments are determined and analyzed for the ground and excited electronic states. We examine the prospects for ion-neutral reactive processes and the production of molecular ions via spontaneous radiative association and laser-induced photoassociation. After that, spontaneous and stimulated blackbody radiation transition rates are calculated and used to obtain radiative lifetimes of vibrational states of the ground and first-excited electronic states. The present results pave the way for the formation and spectroscopy of calcium–alkali-metal-atom molecular ions in modern experiments with cold ion–atom mixtures.

Prospects for a polar-molecular-ion optical probe of varying proton-electron mass ratio

Molecules with deep vibrational potential wells provide optical intervals sensitive to variation in the proton-electron mass ratio ($\mu$). On one hand, polar molecules are of interest since optical state preparation techniques have been demonstrated for such species. On the other hand, it might be assumed that polar species are unfavorable candidates, because typical molecule-frame dipole moments reduce vibrational state lifetimes and cause large polarizabilities and associated Stark shifts. Here, we consider single-photon spectroscopy on a vibrational overtone transition of the polar species TeH$^+$, which is of practical interest because its diagonal Franck-Condon factors should allow rapid state preparation by optical pumping. We point out that all but the ground rotational state obtains a vanishing low-frequency scalar polarizability from coupling with adjacent rotational states, because of a fortuitous relationship between rigid rotor spacings and dipole matrix elements. We project that for good choices of spectroscopy states, demonstrated levels of field control should make possible uncertainties of order $1 \times 10^{-18}$, similar to those of leading atomic ion clocks. The moderately long lived vibrational states of TeH$^+$ make possible a frequency uncertainty approaching $1 \times 10^{-17}$ with one day of averaging for a single trapped ion. Observation over one year could probe for variation of $\mu$ with a sensitivity approaching the $1 \times 10^{-18}/\textrm{yr}$ level.

Erratum: "Accurate potential energy, dipole moment curves, and lifetimes of vibrational states of heteronuclear alkali dimers" [J. Chem. Phys. 140, 184315 (2014)

Erratum: "Accurate potential energy, dipole moment curves, and lifetimes of vibrational states of heteronuclear alkali dimers" [J. Chem. Phys. 140, 184315 (2014)

Measurement of the lifetimes of vibrational states of DNA molecules in functionalized complexes of semiconductor quantum dots

Complexes of self-organized isolated semiconductor crystalline nc-Si/SiO2 quantum dots functionalized with short oligonucleotides are unique objects for revealing the manifestation of new quantum-size effects. It is shown that the observation of narrow spectral lines in micro-Raman scattering spectra of high spectral resolution makes it possible to determine the characteristic time scale of vibrational excitations of nucleotide molecules. The possibility of quantitative investigation into the structural-dynamic properties of fast vibrational processes in biomacromolecules is established.

Ab initio calculations of spectroscopic constants and vibrational state lifetimes of diatomic alkali-alkaline-earth cations.

We investigate the lifetimes of vibrational states of diatomic alkali-alkaline-earth cations to determine their suitability for ultracold experiments where long decoherence time and controllability by an external electric field are desirable. The potential energy and permanent dipole moment curves for the ground electronic states of LiBe+, LiMg+, NaBe+, and NaMg+ are obtained using the coupled cluster with singles doubles and triples and multireference configuration interaction methods in combination with large all-electron cc-pCVQZ and aug-cc-pCV5Z basis sets. The energies and wave functions of all vibrational states are obtained by solving the Schrödinger equation for nuclei with the B-spline basis set method. To predict the lifetimes of vibrational states, the transition dipole moments, as well as the Einstein coefficients describing spontaneous emission, and the stimulated absorption and emission induced by black body radiation are calculated. Surprisingly, in all studied ions, the lifetimes of the highest excited vibrational states are similar to the lifetimes of the ground vibrational states indicating that highly vibrationally excited ions could be useful for the ultracold experiments requiring long decoherence time.

MRCI+Q calculations on spectroscopic properties of excited states of PbH including spin-orbit coupling

The 10 Ʌ-S states associated with the lowest four dissociation limits of PbH radical have been studied utilizing configuration interaction method. For better accuracy, the Davidson correction, core-valence correlation and spin-orbit coupling effects are included. The potential energy curves of 10 Ʌ-S states and 18Ω states have been obtained and characterized. The computed dipole moments of 10 Ʌ-S states are used to reveal the ionic characteristics of the Ʌ-S states. Finally, the transitional dipole moments of several bound Ω states and lifetimes of vibrational states trapped in excited bound Ω states are determined.

Diffusion Rates for Hydrogen on Pd(111) from Molecular Quantum Dynamics Calculations.

The van Hove formula for the dynamical structure factor (DSF) related to particle scattering at mobile adsorbates is extended to include the relaxation of the adsorbates' vibrational states. The total rate obtained from the DSF is assumed to be the sum of a diffusion and a relaxation rate. A simple kinetic model to support this assumption is presented. To illustrate its potential applicability, the formula is evaluated using wave functions, energies, and lifetimes of vibrational states obtained for H/Pd(111) from first-principle calculations. Results show that quantum effects can be expected to be important even at room temperature.

Accurate potential energy, dipole moment curves, and lifetimes of vibrational states of heteronuclear alkali dimers.

We calculate the potential energy curves, the permanent dipole moment curves, and the lifetimes of the ground and excited vibrational states of the heteronuclear alkali dimers XY (X, Y = Li, Na, K, Rb, Cs) in the X(1)Σ(+) electronic state using the coupled cluster with singles doubles and triples method. All-electron quadruple-ζ basis sets with additional core functions are used for Li and Na, and small-core relativistic effective core potentials with quadruple-ζ quality basis sets are used for K, Rb, and Cs. The inclusion of the coupled cluster non-perturbative triple excitations is shown to be crucial for obtaining the accurate potential energy curves. A large one-electron basis set with additional core functions is needed for the accurate prediction of permanent dipole moments. The dissociation energies are overestimated by only 14 cm(-1) for LiNa and by no more than 114 cm(-1) for the other molecules. The discrepancies between the experimental and calculated harmonic vibrational frequencies are less than 1.7 cm(-1), and the discrepancies for the anharmonic correction are less than 0.1 cm(-1). We show that correlation between atomic electronegativity differences and permanent dipole moment of heteronuclear alkali dimers is not perfect. To obtain the vibrational energies and wave functions the vibrational Schrödinger equation is solved with the B-spline basis set method. The transition dipole moments between all vibrational states, the Einstein coefficients, and the lifetimes of the vibrational states are calculated. We analyze the decay rates of the vibrational states in terms of spontaneous emission, and stimulated emission and absorption induced by black body radiation. In all studied heteronuclear alkali dimers the ground vibrational states have much longer lifetimes than any excited states.

Measuring vibrational coherence lifetimes in liquid methanol using transient coherent Raman scattering

We demonstrate the measurement of vibrational coherence in liquids using transient coherent Raman scattering. This technique measures the coherence lifetime of vibrational states through the interference of time-delayed coherent Raman-scattered photons using low-power, non-resonant optical pulses. We measure the vibrational lifetime of the 1033 cm−1 mode in liquid methanol. The resulting lifetime agrees with frequency-domain lineshape measurements. This technique is a complementary and in some cases simpler alternative to standard nonlinear spectroscopy techniques.

A femtosecond velocity map imaging study on B-band predissociation in CH3I. II. The $2_0^1$21 and $3_0^1$31 vibronic levels

Femtosecond time-resolved velocity map imaging experiments are reported on several vibronic levels of the second absorption band (B-band) of CH(3)I, including vibrational excitation in the ν(2) and ν(3) modes of the bound (3)R(1)(E) Rydberg state. Specific predissociation lifetimes have been determined for the 2(0)(1) and 3(0)(1) vibronic levels from measurements of time-resolved I*((2)P(1/2)) and CH(3) fragment images, parent decay, and photoelectron images obtained through both resonant and non-resonant multiphoton ionization. The results are compared with our previously reported predissociation lifetime measurements for the band origin 0(0) (0) [Gitzinger et al., J. Chem. Phys. 132, 234313 (2010)]. The result, previously reported in the literature, where vibrational excitation to the C-I stretching mode (ν(3)) of the CH(3)I (3)R(1)(E) Rydberg state yields a predissociation lifetime about four times slower than that corresponding to the vibrationless state, whereas predissociation is twice faster if the vibrational excitation is to the umbrella mode (ν(2)), is confirmed in the present experiments. In addition to the specific vibrational state lifetimes, which were found to be 0.85 ± 0.04 ps and 4.34 ± 0.13 ps for the 2(0)(1) and 3(0)(1) vibronic levels, respectively, the time evolution of the fragment anisotropy and the vibrational activity of the CH(3) fragment are presented. Additional striking results found in the present work are the evidence of ground state I((2)P(3/2)) fragment production when excitation is produced specifically to the 3(0)(1) vibronic level, which is attributed to predissociation via the A-band (1)Q(1) potential energy surface, and the indication of a fast adiabatic photodissociation process through the repulsive A-band (3)A(1)(4E) state, after direct absorption to this state, competing with absorption to the 3(0)(1) vibronic level of the (3)R(1)(E) Rydberg state of the B-band.

Time-resolved dissociation of the H 2–OH entrance channel complex

Time-resolved experiments and calculations are reported for the predissociation dynamics of the metastable v OH=2 vibrational state of H 2–OH and D 2–OH in their ground electronic states. Good agreement between theory and experiment is found for the absolute lifetimes of H 2–OH and relative product state distributions for D 2–OH. The excited vibrational state lifetimes are 10 −9 and 10 −6 s for the complexes containing D 2 and H 2, respectively.

Peer Reviewed: Stimulated Emission Sepctroscopy in the Time Domain

ADVERTISEMENT RETURN TO ISSUEPREVFeaturesNEXTPeer Reviewed: Stimulated Emission Sepctroscopy in the Time Domain Time-resolved stimulated emission spectroscopy provides the opportunity to measure vibrational state lifetimes in systems where such measurements have previously not been possible G. J. BlanchardCite this: Anal. Chemi. 1997, 69, 11, 351A–357APublication Date (Web):June 1, 2011Publication History Published online1 June 2011Published inissue 1 June 1997https://doi.org/10.1021/ac9716587RIGHTS & PERMISSIONSArticle Views67Altmetric-Citations4LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (11 MB) Get e-Alerts Get e-Alerts

High resolution near infrared spectroscopy of HCl–DCl and DCl–HCl: Relative binding energies, isomer interconversion rates, and mode specific vibrational predissociation

Both D- and H-bonded isomers of the mixed dimers formed between HCl and DCl are investigated via high resolution infrared difference frequency and diode laser spectroscopy in the 2885 and 2064 cm−1 regions. From an analysis of the relative integrated absorption intensities, the D-bonded complex (i.e., HCl–DCl) is determined to be more stable by 16±4 cm−1 than the H-bonded (i.e., DCl–HCl) species. All four chlorine isotopic combinations of the lower energy (HCl–DCl) complex are probed via excitation of both HCl (vHClacc=1←0) and DCl (vDCldon=1←0) stretches. Additionally, two chlorine isotopomers of the higher energy (DCl–HCl) complex are investigated through HCl excitation. Compared to the facile tunneling observed in both (HCl)2 or (DCl)2 complexes, these mixed dimers exhibit more rigid behavior characteristic of two distinct isomeric species. However, the relatively small energy difference (16±4 cm−1) between the two isomers still allows the wave functions for both species to sample both the HCl–DCl and DCl–HCl local minima on the potential surface. This intermediate level of angular localization of the wave function is modeled via 3D quantum mechanical calculations including all three internal rotor angular degrees of freedom. Additionally, a 1D treatment along the minimum energy tunneling path is investigated, which quantifies the asymmetry in the tunneling coordinate due to isotopic dependence of the H- and D-bonded zero point bending and torsion energies. Vibrational predissociation lifetimes in excess of the slit jet instrument line shape are determined from homogeneous broadening of the spectral line widths. The HCl stretch excited lifetime of H-bonded DCl–HCl [ΔνHCldon=44(6) MHz, τHCldon=3.6(5) ns] is threefold shorter than the corresponding lifetime of D-bonded HCl–DCl [ΔνHClacc=16(3) MHz, τHClacc=9.6(16) ns]. This ratio is quite comparable to the results obtained in investigations of (HCl)2 and consistent with a stronger, mode specific coupling to the dissociation coordinate for excitation of the bonded-HX vs free-HX moiety. However, the absolute lifetimes of both vHClacc=1 HCl–DCl and vHCldon=1 DCl–HCl complexes are tenfold shorter than the corresponding excited vibrational state lifetimes in (HCl)2. This suggests a near resonant channel for predissociation into HCl(v=0)+DCl(v=1) which minimizes the energy deposited into rotation and relative translation of the diatomic fragments.

Microscopic theory of gas-surface interaction

A kinetic theory for inelastic scattering, trapping and desorption of gas molecules by surfaces is described. The theory is valid if the time scale τ l = 1/r introduced by the relaxation ratesr in the kinetic equations (which is of the order of the life time of vibrational states of adsorbates) is sufficiently large compared to the vibrational period τ0. For sufficiently large activation energies of the adsorbates another time constant τres, the residence time of adsorbed particles, can be determined from the theory. One thus may distinguish four different partly overlapping regimes defined by the time scalest I≪τ l , τ0≪tII, τ l ≪tIII and τres≪tIV. Regime I is governed by the Schrodinger equation regime II by the kinetic equations. In the region where both regimes overlap the kinetic coefficients can be expressed in terms of microscopic quantities which have been calculated previously. The relevant quantities in the other regimes are introduced and discussed from a unified point of view thus providing a link between the regimes I and IV which have been treated in detail before.

Dissociative excitation of water by metastable argon

The reaction Ar( 2P 2,0) + H 2O → Ar + H + OH(A 2Σ +)was studied in crossed molecular beams by observing the luminescence from OH(A 2Σ +). No significant dependence of the spectrum on collision energy was found over the 22–52 meV region. Spectral simulation was used to obtain the OH(A) vibrational distribution and rotational temperature, assuming a Boltzmann rotational distribution. Since predissociation is known to strongly affect the rovibrational distribution, the individual rotational state lifetimes were included in the simulation program and were used to obtain the average vibrational state lifetimes. Excellent agreement with experiment was obtained for vibrational population ratios N 0/ N 1/ N 2 of 1.00/ 0.40/0.013 and a rotational temperature of 4000 K. Correction for the different average vibrational lifetimes gave formation rate ratios P 0/ P 1/ P 2 of 1.00/0.49/0.25. The differences between these results and those from flowing afterglow studies on the same system are discussed. Three reaction mechanisms are considered, and the vibrational prior distributions are calculated from a simple density-of-states model. Only fair agreement with experiment is obtained. The best agreement for the mechanisms giving OH(A) in two 2-body dissociation steps is obtained by assuming 1.0 eV of internal energy remains in the second step. The OH(A) vibrational population distribution of the present work is similar to that found in the photolysis of H 2O at 122 nm, where there is 1.10 eV of excess internal energy.

Collective vibrations of closed-shell nuclei

Collective vibrations in atomic nuclei are studied, assuming a time-dependent nuclear well potential. The collective frequencies (and the collective paramters B λ and C λ ) are obtained by imposing the condition of time-independence on the expectation value of the energy. The calculations are carried through without the use of the adiabatic approximation. For some closed-shell nuclei it is found that the lowest vibrational state should not be of the quadrupole type. The life-times of vibrational states are also calculated. The related problem of static deformations of a finite well potential is discussed. Some numerical results for the quadrupole and octupole vibrations in O 16 and the quadrupole vibration in Si 28 are given.