Gravity generated by large masses has been observed using a variety of probes from atomic interferometers to torsional balances. However, gravitational coupling between small masses has never been observed so far. Here, we demonstrate sensitive displacement sensing of the Brownian motion of an optically trapped 7-mg pendulum motion whose natural quality factor is increased to 10 8 through dissipation dilution. The sensitivity for an integration time of one second corresponds to the displacement generated by the gravitational coupling between the probe and a mm separated 100 mg mass, whose position is modulated at the pendulum mechanical resonant frequency. Development of such a sensitive displacement sensor using a mg-scale device will pave the way for a new class of experiments where gravitational coupling between small masses in quantum regimes can be achieved.
We calculated the fundamental and overtone OH stretching vibrational spectra for the following alcohols and acidsmethanol, ethanol, 1-propanol, 2-propanol, tert-butyl alcohol, 2,2,2-trifluoroethanol, acetic acid, trifluoroacetic acid, and nitric acidunder the local mode model. We obtained the potential energy surface (PES) and the dipole moment function (DMF) by hybrid density functional theory method and performed vibrational calculation using the grid variational method. The theoretical results were in good agreement with the experimental observations. It was found that the molecular shape, such as the rotational conformation, is very important in the description of the OH stretching vibrational spectra. For alcohols with rotational conformers, such as ethanol, 1-propanol, and 2-propanol, we found that the isomer with the alkyl group in the trans position of the vibrating OH bond has a larger transition energy and a slightly stronger absorption intensity. We analyzed the first and second derivative terms of the DMF of these molecules to obtain insight on the difference in the absorption intensities. In addition, for the fundamental spectra, we investigated the difference between the local and normal mode vibrational calculation results.
The intensity of the CH stretching overtone spectra of liquid cis-dichloroethylene is known to be greater than that of the trans isomer, even though the transition energies are almost the same. To obtain theoretical insight on this feature, we performed a vibrational calculation under the local mode model, which is preferred for describing vibration of light−heavy bonds, using the grid method and the potential energy surface (PES) and the dipole moment function (DMF) calculated by hybrid density functional theory method. It was determined that the DMF, in the direction perpendicular to the CC bond, was significantly distorted from linearity as a function of the CH bond length. This distortion, which is regarded as the electric anharmonicity, was greater for the cis isomer, thus giving a stronger overtone absorption intensity for this isomer. In addition, the numerical accuracy in representing the PES and DMF was discussed for the overtone vibrational calculation.
We presented a theoretical method for controlling quantum dynamics by locally optimized nonstationary laser fields, within the semiclassical theory of the molecule–radiation field interaction. The external laser field is optimized based on the control theory of a linear time-invariant (LTI) system, so that both the summation of the population of the nontarget states and the total energies of the laser fields are minimized. The optimization procedure involves operation of the so-called feedback gain matrix to the time-dependent state vector. This procedure is carried out at every successive short stage, in which the time-dependent Schrödinger equation can be approximated to the equation of motion of the LTI system. As an example, the control theory was applied to laser-induced ring-puckering isomerization, the dynamics of which can be described as the wave packet in the one-dimensional double minimum potential under locally optimized laser fields. The result indicated that nearly 100% of the population can be transferred to the final product state by irradiation of the optimized laser fields. The optimized laser fields were analyzed to obtain information on the carrier frequencies or the frequency modulation by using the fast Fourier transform method. These results were then compared with the result of isomerization induced by nonoptimized laser fields.
Articles you may be interested inA hybrid local/global optimal control algorithm for dissipative systems with time-dependent targets: Formulation and application to relaxing adsorbates A general local control theory for manipulating quantum system dynamics is developed. Basic concept of the present theory is lying in the realization of monotonous increasing condition of the performance index, which is locally ͑in time domain͒ defined to major how the present quantum state satisfies the current objective. The local control field is designed to satisfy the above condition taking into account the equation of motion of the system. It is found, through the formulation, that the monotonous increasing condition can be achieved as long as the performance index is given as a function of expectation values of time-dependent observable operators, whose equation of motion is governed by the field-free system Hamiltonian or Liouvillian. It is also shown that the present theory is a generalization of the local optimization approach which has been successfully applied to many of molecular dynamics control problems. As for the special cases, performance indices for ''transition path control,'' ''population distribution control,'' and ''wave packet shaping'' are proposed. The theory is applied to vibrational control problems of the one-dimensional model system of hydrogen fluoride. The results show that the present method works effectively for the population dynamics control as well as the wave packet shaping.
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