Quantum computation with vibrationally excited molecules

A new physical implementation for quantum computation is proposed. The vibrational modes of molecules are used to encode qubit systems. Global quantum logic gates are realized using shaped femtosecond laser pulses which are calculated applying optimal control theory. The scaling of the system is favorable; sources for decoherence can be eliminated. A complete set of one- and two-quantum gates is presented for a specific molecule. Detailed analysis regarding experimental realization shows that the structural resolution of today's pulse shapers is easily sufficient for pulse formation.     

Microwave spectroscopy of furfural in vibrationally excited states

The results of microwave spectrum investigation of the excited vibrational states of furfural in the frequency range between 49 and 149 GHz are reported. In total 15 excited vibrational states (9 for trans-furfural and 6 for cis-furfural) were assigned and analyzed. Six of the 15 investigated states were assigned for the first time. Accurate values of rigid rotor and quartic centrifugal distortion constants of asymmetric top Hamiltonian have been determined for 13 excited states. Also for some states several sextic and octic level constants were needed in order to fit the data within experimental accuracy. The v_t = 3 and v_s = 1, v_a = 1 states of trans-furfural were found to be strongly perturbed and only rotational transitions with low K_a values can be reliably identified in this study.     

Collisional deactivation of vibrationally excited triplet molecules of fluorenone

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 4, pp. 607–612, October, 1991.     

Microwave spectra of thionyl fluoride in vibrationally excited states

The microwave spectrum has been observed and rotational constants obtained for the v₄ = 1 and v₆ = 1 vibrationally excited states of thionyl fluoride. The perturbation of the C rotational constant is explained in terms of a Coriolis resonance between these levels.     

Millimeter wave spectroscopy of OCS in vibrationally excited states

The millimeter wave transitions of OCS in the range of J = 9-8 to 12-11 were measured with an accuracy of 10 kHz for the vibrational states 2ν₂, 3ν₂, 4ν₂, ν₁, ν₁ + ν₂, ν₁ + 2ν₂, and ν₁ + 3ν₂ of the normal species and ν₂, 2ν₂, and 3ν₂ of OC³⁴S. An anomalous behavior of the centrifugal distortion constant was observed and interpreted as due to the l-type resonance between the sublevels with different l values. The unperturbed values of the centrifugal distortion and l-type doubling constants and the vibrational intervals between sublevels were determined.     

Microwave spectra of phosphoryl trifluoride in vibrationally excited states

The ground-state rotational spectra of ¹⁶OPF₃ and ¹⁸OPF₃ have been recorded and analysed to yield a structure and accurate centrifugal distortion constants.

The pure rotational spectrum of ¹⁶OPF₃ has been recorded and analysed for five of the molecule's vibrationally excited states. The analysis of the ν₅ = 1 and ν₆ = 1 states is discussed in detail and values of ζ₅₅ ^z and ζ₆₆ ^z have been obtained. In addition, information is obtained about the elusive A rotational constant for ν₆ = 1 due to an accidental near degeneracy which yields the value A _ν=4797·86 MHz.

Some of the information obtained is used to derive the harmonic force field for the OPF₃ molecule. The use of ground-state distortion constants instead of their equilibrium values is discussed.     

Collision relaxation cross section of highly vibrationally excited molecules

Through quantum-beat spectroscopy collision relaxation of a high vibrational level of SO2 at 44 877.52 cm(-1) is characterized. This is a first measurement of collision relaxation for a single, highly excited vibrational level. The deduced relaxation cross section of this excited level by Ar is 216 A(2), 5 times the area of the hard sphere, and by an ambient temperature SO2 molecule is 969 A(2), almost 20 times the hard sphere. These cross sections indicate that relaxation collisions of highly vibrationally excited molecules have effective distances much longer than van der Waals radii and involve mechanisms qualitatively different from lower excitations.     

Symmetry-resolved absorption spectra of vibrationally excited CO2 molecules

Symmetry-resolved x-ray absorption spectroscopy has been first carried out on high-temperature molecules. From the angle-resolved ion yield spectra of CO2 both at room temperature and at 430 degrees C, symmetry-resolved absorption profiles of the C 1s(-1) 2pi(u) and O 1s(-1) 2pi(u) resonances have been extracted for the vibrational ground state molecules and bending-vibration excited ones. The profiles change dramatically between them, and the Renner-Teller effect becomes more evident for the vibrationally excited molecules. The effects of the multimode vibronic coupling are suggested for the O 1s(-1) 2pi(u) and O 1s(-1) 3s sigma(g) resonances.     

Electron impact cross sections of vibrationally and electronically excited molecules

It is well known that the electron impact cross sections for elastic and inelastic processes for the vibrationally and electronically excited molecules are predominantly different than those for molecules in the ground state. Collisions of low energy electrons with excited molecules play an important role in explaining the behavior of gas discharges in laser and plasma physics, in planetary atmospheres, stars, and interstellar medium and in plasmas widely used in the fabrication of microelectronics. This explains as to why there is a need for having validated sets of electron impact cross sections for different processes. This work reviews the subject of electron collisions with vibrationally and electronically excited molecules in a comprehensive way. The survey has been carried out for a few excited molecules such as H₂, D₂, T₂, HD, HT, DT, N₂, O₂, and CO₂.     

Dissociative attachment of low-energy electrons to vibrationally excited hydrogen molecules

Dissociative electron attachment to hot hydrogen molecules is studied in the framework of nonlocal resonance model. The method based on the use of the Bateman approximation, well known in nuclear physics, is adapted for solving the Lippmann-Schwinger integral equation of the nonlocal resonance model and applied to the calculation of cross sections of inelastic resonant electron-molecule collisions. The proposed method is compared with the Schwinger-Lanczos algorithm used extensively for the treatment of these processes. It is shown that the Bateman approximation is very useful and efficient for treating the non-separable nonlocal potentials appearing in the integral kernels of the nonlocal resonance models. The calculated cross sections for the dissociative attachment of electrons to vibrationally excited hydrogen molecules are of importance for astrophysics. This paper is dedicated to Prof. J. Bičák on the occasion of his 60th birthday.     

Stark spectrum of barium in highly excited Rydberg states

We present observations of Stark spectra of barium in highly excited Rydberg states in the energy region around n = 35. The one-photon excitation concerns the π transition. The observed Stark spectra at electric fields ranging from 0 to 60 V·cm-1 are well explained by the diagonalization of the Hamiltonian incorporating the core effects. From the Stark maps, the anti-crossings between energy levels are identified experimentally and theoretically. The time of flight spectra at the specified Stark states are recorded, where the deceleration and acceleration of barium atoms are observed. This is very consistent with the prediction derived from the Stark maps from the point of view of energy conservation.     

微波场中里德堡锂原子的高激发跃迁

运用含时多态展开方法研究微波场中里德堡锂原子高激发态的性质,得到锂原子在微波场中的跃迁几率,实现对量子态的操纵与控制.结果表明:选择合适的振幅、频率等参数,可以实现布居数在量子态之间的完全跃迁.     

啁啾微波场中里德伯钠原子高激发态的布居跃迁

采用含时多态展开方法, 结合B样条函数和单电子原子模型势研究微波场中钠原子里德伯高激发态的性质, 得到钠原子的能级结构及在微波场中的布居数迁移, 实现对量子态的操纵与控制. 结果表明: 含时多态展开方法结合B样条函数和单电子原子模型势是有效研究微波场中碱金属原子性质的一种方法; 选择合适的啁啾率、振幅等参数, 可以实现布居数在量子态之间的完全迁移和量子态囚禁.     

微波场中里德堡锂原子的高激发跃迁

运用含时多态展开方法研究微波场中里德堡锂原子高激发态的性质,得到锂原子在微波场中的跃迁几率,实现对量子态的操纵与控制。结果表明：选择合适的振幅、频率等参数,可以实现布居数在量子态之间的完全跃迁。     

Dissociation of vibrationally excited heteronuclear molecules by an intense infrared field

Results of numerical simulations of the vibrational-rotational dynamics of a molecular system in the field of an intense infrared laser pulse are presented. The cases of quasi-monochromatic and ultrashort laser action on the nuclear subsystem are considered. The influence of the coherent repopulation of vibrationally excited molecular states on photodissociation and the peculiarities of photodissociation under the action of an ultrashort laser pulse are discussed. The results obtained for quasi-monochromatic laser action are interpreted in terms of interference stabilization.     

Millimeter- and submillimeter-wave spectroscopy of HBS and DBS in vibrationally excited states

Normal and deuterated isotopic variants of thioborine have been produced in the gas phase by a high temperature reaction between crystalline boron and hydrogen sulfide. Millimeter- and submillimeter-wave rotational spectra have been recorded in the frequency range from 75 to 730 GHz for vibrational ground and excited states of the H^10/11B³²S and D^10/11B³²S isotopic species. The spectra of all the excited states which lie below 1500 cm⁻¹, that are 01¹0, 00⁰1, 02⁰0, and 02²0, have been observed and analyzed for each of the four isotopologues investigated. High-order Fermi resonance parameters were found important to analyze properly the spectra of the 00⁰1 and 02⁰0 interacting states. The improved rotational data in conjunction with earlier infrared spectroscopy results have been employed to calculate more precise anharmonic force constants and equilibrium bond lengths.     

Grazing incidence scattering of vibrationally excited H2 molecules from metal surfaces

We have studied the scattering of vibrationally excited H₂ molecules from metal surfaces under fast grazing incidence conditions, by means of quasi-classical calculations based on six-dimensional potential energy surfaces. We show that, in spite of the fast parallel motion, the reorientation of the molecule along the trajectory plays a fundamental role on the scattering, being responsible for the nonmonotonic behavior observed as a function of the normal incidence energy, similar to that observed under slow normal incidence conditions. The present study has allowed us to further prove that the interaction between a H₂ molecule and an ordered metal surface under fast grazing incidence conditions is, in general, governed by the normal momentum of the molecule.