Search results for "Stark effect"
showing 10 items of 67 documents
A quantum dynamics study of the benzopyran ring opening guided by laser pulses
2014
Abstract The ring-opening photoisomerization of benzopyran, which occurs via a photochemical route involving a conical intersection, has been studied with quantum dynamics calculations using the multi-configuration time-dependent Hartree method (MCTDH). We introduce a mechanistic strategy to control the conversion of benzopyran to merocyanine with laser pulses. We use a six-dimensional model developed in a previous work for the potential energy surfaces (PES) based on an extension of the vibronic-coupling Hamiltonian model (diabatization method by ansatz), which depends on the most active degrees of freedom. The main objective of these quantum dynamics simulations is to provide a set of str…
Full-dimensional control of the radiationless decay in pyrazine using the dynamic Stark effect
2014
We present a full quantum-mechanical study of the laser control of the radiationless decay between the B3u(nπ(*)) and B2u(ππ(*)) states of pyrazine using the dynamic Stark effect. In contrast to our previous study [Sala et al., J. Chem. Phys. 140, 194309 (2014)], where a four-dimensional model was used, all the 24 degrees of freedom are now included in order to test the robustness of the strategy of control. Using a vibronic coupling Hamiltonian model in a diabatic representation, the multi-layer version of the multi-configuration time-dependent Hartree method is exploited to propagate the corresponding wave packets. We still observe a trapping of the wavepacket on the B2u(ππ(*)) potential …
Dipole moments of 4′-aminoflavonols determined using electro-optical absorption measurements or molecular Stark-effect spectroscopy
2002
The electro-optical absorption measurements (EOAM) were used to measure the dipole moments of the normal form of 4 � -(methoxy)-3hydroxyflavone (FOM), 4 � -(dimethylamino)-3-hydroxyflavone (FME), and 4 � -N-(15-azacrown-5)-3-hydroxyflavone (FCR). For these probes the excited state intramolecular proton transfer (ESIPT) takes place. For comparison, the dipole moments of 4 � -(dimethylamino)-3methoxyflavone (FME3ME), for which ESIPT is lacking, were measured. In the case of FCR, FME, and FME3ME the equilibrated ground (µg) and excited Franck–Condon state (µ FC ) electrical dipole moments are parallel to each other and also parallel to the transition dipole moment. The electrical dipole moment…
Molecular Stark-effect spectroscopy of Prodan and Laurdan in different solvents and electric dipole moments in their equilibrated ground and Franck–C…
2007
Abstract The results from electrooptical absorption measurements (EOAM) on the ground and excited Franck–Condon state dipole moments of Prodan and Laurdan in 1,4-dioxane and cyclohexane are presented. The ground and excited Franck–Condon state electric dipole moments as well as the respective transition moment of both probes are parallel. The electric dipole moments of Prodan and Laurdan in the ground state in cyclohexane and 1,4-dioxane have values within the range (15.7–16.5) × 10 −30 C m. On optical excitation the dipole moments increase by (42.1–49.5) × 10 −30 C m. The obtained results are compared with the values of the dipole moments of Prodan and Laurdan determined by other methods.
Electric field induced alignment-orientation conversion in diatomic molecules: analysis and observation for NaK
1999
This article reports the observation of the molecular fluorescence circularity under irradiation with linearly polarised light. This alignment-orientation conversion phenomenon arises as a result of partial transformation from alignment of the ensemble of 1 P state molecular angular momenta into their orientation under the effect of non-linear dc Stark effect. Circularity rate up to 0.12 was observed in D 1 P! X 1 S fluorescence of 23 Na 39 K molecules in agreement with the theoretically predicted value.
Studies of rotational level Λ-doubling by rf-optical double resonance spectroscopy: application to NaK D1Π
1997
Abstract We report here the application of optical-radio frequency double resonance spectroscopy for individual rotational levels of the NaK D 1 Π state. Lambda doubling constant q values for five ν′, J ′ levels are obtained. These data are combined with measurements of dc e - f Stark-mixing-induced changes in optical spectra, and the electric dipole moment d p in the D 1 Π state is determined.
Photoinduced optical anisotropy in organic molecular films controlled by an electric field
1993
Abstract The photoinduced reorientation of dye molecules in molecular films on solid substrates has been controlled with external dc electric fields, leading to solid state structures, which are macroscopically polar, temporally stable at room temperature, and well-defined at the molecular level. A simulation based on the excitation-driven rotational diffusion of the molecules in the potential of their neighbors yielded a realistic model and indicated a collective character of the process. This shows that we are close to a quantitative comprehension of the molecular interactions within these films.
Stark level crossing and optical-rf double resonance in NaK D 1 Π
1997
We report here (Lambda) -doubling splitting and permanent electric dipole moment d p measurements for a number of vibrotational levels of NaK D 1 II state. Two different methods, which are not Doppler limited, were used. Stark effect induced level crossing was registered as fluorescence polarization changes with external electric field, which allowed us to obtain, from one fit, the values of electric dipole moment and (Lambda) -doubling splitting (Delta) ef between e, f substates of an individual rotational state. Another method consisted in obtaining the ratio (Delta) ef /d p from electric field dependence of the intensity of forbidden line appeared in fluorescence as a result of e- f Star…
Experimental Stark broadening studies of the CI transition 3s 1 P 1o − 3p 1 S 0 at 833.5 nm
2011
AbstractExperimental Stark broadening studies of the infrared CI transition 3s 1 P 1o − 3p 1 S 0 at 833.5 nm are reported for the first time. A high-current wall-stabilized arc, operated in a mixture of helium, argon, carbon dioxide and hydrogen, was applied as the plasma source. Radiation emitted from homogeneous and optically thin plasma layers was analyzed. Stark broadening studies of the selected CI transition and the hydrogen Balmer β line were performed. As expected from theoretical considerations, the CI line width depends linearly on the electron density of the plasma. Applying theoretical Stark broadening data for the Hgb line, the measured Stark widths of the CI line were calibrat…
Stark broadening of the hydrogen Paschen ? transition at electron densities of the order of $ \mathsf {10^{15}}$ cm $ \mathsf {^{-3}}$
2003
Stark broadening measurements and calculations of the Paschen γ spectral line of hydrogen ( λ = 1.094[: MU :] m) are reported. Investigations have been performed at plasma electron densities between 1.4×10 15 cm -3 and 3.7×10 15 cm -3 . As the light source a wall-stabilized arc operated in a helium-hydrogen gas mixture at atmospheric pressure has been applied. The radiation of the plasma emitted from nearly homogeneous plasma layers in end-on direction, was measured with the use of a grating spectrometer equipped with a charge coupled device (CCD) detector. The radiance calibration was carried out against light outputs originating from a tungsten strip radiation standard. The measured FWHM …