Lowest Vibronic State Research Articles

Quantum model of dynamic Stark‐induced degenerate vibronic state by two nonresonant shift‐up lasers for π‐electron angular momentum generation

AbstractA theoretical scenario for the generation of coherent π‐electron angular momentum in a low‐symmetry aromatic molecule using two nonresonant shift‐up lasers is presented. The effects of vibrational modes on coherent π‐electron angular momentum are considered in the adiabatic approximation. In this scenario, two electronic excited states are irradiated with two linearly polarized nonresonant lasers. This causes a consistent up‐shift in the vibronic energy levels of each electronically excited state toward higher energy as a result of the dynamic Stark effect. For the weak coupling case of the electronic‐vibrational interactions, the lowest vibronic states in the two electronic excited states are designed to be degenerate by varying the parameters (frequency and intensity) of each laser. The resultant degenerate state, called the dynamic Stark‐induced degenerate vibronic state (DSIDVS), is the origin of the coherent π‐electron angular momentum generation. An optimal laser parameter set is determined under conditions in which the lowest two vibronic states form the DSIDVS. The DSIDVS was formulated by the method of Laplace transformations. An analytical expression for the coherent π‐electron angular momentum was derived in the displaced harmonic oscillator model. We examined the dependence of the time‐averaged z‐component of the coherent angular momentum on the ratio of the two detunings and potential displacements of toluene, a typical low‐symmetry aromatic ring molecule, which belongs to the weak coupling case and is adopted to demonstrate the theoretical scenario. The inclusion of potential displacements in the angular momentum generation was found to reduce the value of by half, compared with that in the frozen nuclear approximation.

Resonance enhanced two-photon ionization spectrum of ultracold 85Rb133Cs molecules in [formula omitted] transitions

We present resonance enhanced two-photon ionization (RETPI) spectrum between 14,500 and 15850 cm−1 for ultracold ground state 85Rb133Cs molecules. With an assistant of optical pumping from one 1070nm laser, (2)1Π1←X1Σ+ electronic transition is distinguished from (4)3Σ+←a3Σ+ and (3)3Π←a3Σ+ transitions. Some observed RETPI spectra are globally assigned to vibrational transitions from X1Σ+(v=0−5) to (2)1Π1(v=5−20). Based on these assignments, the spectroscopic constants of X1Σ+ and (2)1Π1 are simultaneously derived, including energy separation, harmonic and anharmonic constants. Then a map of Franck-Condon factors between vibrational transitions of X1Σ+(v=0−9) and (2)1Π1(v=0−20) is plotted based on these constants. Our present work would be meaningful for continuous accumulation of ultracold 85Rb133Cs molecules in the lowest vibronic state with further optical pumping.

Dynamics of selected rovibronic eigenstates in the V system of carbon disulfide 12,13CS2

Abstract The dynamics of individual eigenstates of carbon disulfide, 12 CS 2 and 13 CS 2 , resulting from the interaction of rovibronic levels of the 1 B 2 state with background states, have been investigated in the lowest vibronic state 10V. Using time-resolved spectroscopy with FTL nanosecond laser pulses of jet-cooled molecules, eigenstate absorption intensities, linewidths γ = 1/τ = (0.6–6.0) × 10 5 s −1 , and magnetic properties were determined, with the latter measured by Lande g factors of up to 0.04 in 12 CS 2 and hyperfine splittings of up to 10 MHz in 13 CS 2 . The intensities and linewidths were found to be linearly correlated in sets of eigenstates of a rovibronic level. This behaviour revealed the background states to be essentially dark, allowing us to estimate the linewidths of the zero-order states. Hyperfine splittings and g factors show no simple correlation with the intensity, a finding which is attributed to the second-order origin of the background state magnetic properties. Based on the density and the characteristics of the eigenstates, a coupling scheme is proposed, for which the background states represent rovibronic levels of the evs B 2 spin component of the 3 A 2 electronic state interacting with highly excited rovibronic levels of the 1 Σ + g electronic ground state.

Vibronic coupling effects in trimeric mixed-valence clusters

The spectrum of a trimeric mired-valence cluster d1–d1–d2 is calculated in the Piepha-Krausz-Schatz vibronic model. Based on the vibronic spectra obtained magnetic properties of the d1–d1–d2 cluster are investigated It is shown that spin of the system's ground state may change not only as a result of double exchange reduction by vibronic coupling, but also due to a diflerence in the eneqy dependence of the lowest vibronic states on the vibronic coupling constant for diflerent total spin values. Unlike previous studies of vibronic interactions in the d1–d1–d2 cluster, in this study the diagonalizations of the vibronic-coupling and double-exchange matrices are fuljilled simultaneously, using Lanczos' method. Due to this, all types 4 vibronic state mixing by double exchange could be taken into account properly.

Inversion splitting in the T(X)t2 Jahn-Teller system; tunnelling or 'hopping'?

The splitting between the two lowest vibronic states in the T(X)t2 Jahn-Teller system is calculated using two approximations. The first is analytical and is based on an adiabatic one-sheet WKB approximation in which the splitting is due exclusively to tunnelling. The second method is numerical and uses cubic states appropriate to very strong coupling which have been derived previously by a transformation method. The latter calculation is in direct contrast to other numerical methods which use states appropriate to the weak-coupling limit. The second calculation includes both tunnelling and 'hopping' (non-adiabatic mixing processes). Thus, by subtraction of the results from the two methods, the contributions of tunnelling and 'hopping' to the inversion splitting can be obtained.

First observation of an electronically excited state ofLi3

We report the first observation of an excited state of ${\mathrm{Li}}_{3}$. With an origin band at 14 583 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, this state has been identified as ${2}^{2}$E'. Analysis based on the dynamic Jahn-Teller model reveals very weak distortion and localization characteristics (${\mathrm{E}}_{\mathrm{stab}=57}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, ${\mathrm{E}}_{\mathrm{b}}$=17 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, ${\mathrm{\ensuremath{\omega}}}_{0}$=191 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$). The lowest vibronic state is located above the conical intersection, implying a nearly ${\mathrm{D}}_{3\mathrm{h}}$ geometry. The frequency of the completely symmetric mode is 326 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. Analyses of rotational states and Franck-Condon factors are also presented.

Vibronic coupling to T1 and T2 vibrations and the Jahn-Teller effect in transition-metal exchange tetraclusters

A study has been made on the four-center Jahn-Teller effect in tetrahedral transition-metal tetraclusters of M4X4L4 and M4OX6L4 types (M metal, X and L ligands) for twofold orbital degeneracy at each of the four centers and strong coupling between the electronic states there and the cluster vibrations. An analytic expression is derived for the adiabatic potential in the space of all active vibrations. The features of the adiabatic-potential sheets in the T1 and T2 vibration space are examined, and the spectrum is derived for the lowest vibronic states. There is a qualitative discussion of the system dynamics.

Study of the intermediate Jahn-Teller system La2+in CaF2Raman and EPR spectroscopy

New low-temperature vibronic Raman and EPR (under stress) spectra on CaF2:La2+ are reported. The experimental data are interpreted as indicating the presence of an intermediate E(X) epsilon type of Jahn-Teller coupling. The lowest vibronic state is approximately=15 cm-1 below the top of the angular barrier.

Velocity dependence of rotational rainbow structure in Na2–Ar

We present level-to-level differential cross sections for the rotationally inelastic process Na2( ji=7)+Ar→Na2( jf)+Ar at center of mass energies 0.49 and 1.1 eV, with Na2 in its lowest vibronic state. The energy was varied by seeding Na2 in noble gas mixtures of varying atomic mass. The range of the final rotational quantum number jf is 9≤ jf ≤47, corresponding to 2≤Δj≤40. The measurements were made in crossed molecular beams. The initial rotational level was selected using optical pumping, and the final rotational level was detected by laser induced fluorescence. The angular distribution was determined by a new Doppler technique that gives good small angle resolution, and whose indifference to the direction of the initial relative velocity of the collision simplifies measurements at different energies.

Dynamic Jahn-Teller Effect of an Impurity in a Spontaneously Distorted Crystal

The local symmetry of ${\mathrm{Ti}}^{4+}$ sites in SrTi${\mathrm{O}}_{3}$ is known to be cubic above 106\ifmmode^\circ\else\textdegree\fi{}K, and tetragonal below. We have investigated the electron-spin-resonance spectrum of substitutional ${\mathrm{Ni}}^{3+}$ in the tetragonal phase of this compound. The components of the $g$ tensor are observed to vary monotonically from ${g}_{\ensuremath{\perp}}=2.215$ and ${g}_{\mathrm{II}}=2.103$ at 4\ifmmode^\circ\else\textdegree\fi{}K, to ${g}_{\mathrm{II}}={g}_{\ensuremath{\perp}}=2.180$ at 106\ifmmode^\circ\else\textdegree\fi{}K. Three models of the dynamical Jahn-Teller effect in the presence of coupling to strain are examined. The magnitude and temperature dependence of ${g}_{\ensuremath{\perp}}\ensuremath{-}{g}_{\mathrm{II}}$ are best explained by a model in which the $g$ tensor is given by a Boltzmann average over the two lowest vibronic states. The tunneling splitting appears to exceed by far the maximum spontaneous splitting of these states (23 ${\mathrm{cm}}^{\ensuremath{-}1}$). Our results indicate that the elongation of the nearest-neighbor octahedron is too small to be the principal cause of the $g$ splitting.