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Stark rotation

Qotti G, Linnartz H, Meerts W L, van der Avoird A and Oithof E 1996 Stark effeot and dipoie moments of (NH3)2 in different vibration-rotation-tunneiing states J. Chem. Phys. 104 3898-906... [Pg.1262]

A MBER spectrometer is shown schematically in figure C1.3.1. The teclmique relies on using two inhomogeneous electric fields, the A and B fields, to focus the beam. Since the Stark effect is different for different rotational states, the A and B fields can be set up so that a particular rotational state (with a positive Stark effect) is focused onto the detector. In MBER spectroscopy, the molecular beam is irradiated with microwave or radiofrequency radiation in the... [Pg.2440]

Figure 9.24 shows part of the laser Stark spectrum of the bent triatomic molecule FNO obtained with a CO infrared laser operating at 1837.430 cm All the transitions shown are Stark components of the rotational line of the Ig vibrational transition, where Vj is the N-F stretching vibration. The rotational symbolism is that for a symmetric rotor (to which FNO approximates) for which q implies that AA = 0, P implies that A/ = — 1 and the numbers indicate that K" = 7 and J" = 8 (see Section 6.2.4.2). In an electric field each J level is split into (J + 1) components (see Section 5.2.3), each specified by its value of Mj. The selection mle when the radiation is polarized perpendicular to the field (as here) is AMj = 1. Eight of the resulting Stark components are shown. [Pg.369]

The quantum theory of spectral collapse presented in Chapter 4 aims at even lower gas densities where the Stark or Zeeman multiplets of atomic spectra as well as the rotational structure of all the branches of absorption or Raman spectra are well resolved. The evolution of basic ideas of line broadening and interference (spectral exchange) is reviewed. Adiabatic and non-adiabatic spectral broadening are described in the frame of binary non-Markovian theory and compared with the impact approximation. The conditions for spectral collapse and subsequent narrowing of the spectra are analysed for the simplest examples, which model typical situations in atomic and molecular spectroscopy. Special attention is paid to collapse of the isotropic Raman spectrum. Quantum theory, based on first principles, attempts to predict the. /-dependence of the widths of the rotational component as well as the envelope of the unresolved and then collapsed spectrum (Fig. 0.4). [Pg.7]

Fig. 0.5. IR absorption spectra of HC1 in different liquid solvents (a) in SF6 [16] (the triangles mark the positions of the rotational components in the resolved spectrum of the rarefied gas) (b) in He [15] (c) in CCU (the vertical lines mark the frequencies vj and the intensities of the Stark components of the linear rotator spectrum split by the electrical field of the cage)[17]. Fig. 0.5. IR absorption spectra of HC1 in different liquid solvents (a) in SF6 [16] (the triangles mark the positions of the rotational components in the resolved spectrum of the rarefied gas) (b) in He [15] (c) in CCU (the vertical lines mark the frequencies vj and the intensities of the Stark components of the linear rotator spectrum split by the electrical field of the cage)[17].
The envelope of the Stark structure of the rotator in a constant orienting field, calculated quantum-mechanically in [17], roughly reproduces the shape of the triplet (Fig. 0.5(c)). The appearance of the Q-branch in the linear rotator spectrum indicates that the axis is partially fixed, i.e. some molecules perform librations of small amplitude around the field. Only molecules with high enough rotational energy overcome the barrier created by the field. They rotate with the frequencies observed in the... [Pg.9]

The analysis performed allows one to judge qualitatively about the processes, which go on in a spectrum when the Stark structure of rotational transitions is averaged by fluctuations of the orienting field. If y decreases, x being fixed, the resolved Stark structure with the intense Q-branch in the centre transforms into the spectrum of a quasi-free rotator. If x < 1, the spectrum may be singlet in the intermediate region. [Pg.240]

The high value of the electron density at the nucleus leads to the enhancement of the electron EDM in heavy atoms. The other possible source of the enhancement is the presence of small energy denominators in the sum over states in the first term of Eq.(29). In particular, this takes place when (Eo — En) is of the order of the molecular rotational constant. (It is imperative that a nonperturbative treatment be invoked when the Stark matrix element e z(v /0 z v / ) is comparable to the energy denominator (Eq En) [33].) Neglecting the second term of the right-hand side of Eq.(29), which does not contain this enhancement factor [8, 27], we get... [Pg.249]

SSR-504734 is a potent, selective, and reversible inhibitor (IC50 = 18 nM) that is competitive with glycine [47,51]. The inhibitor rapidly and reversibly blocked the uptake of [14C]glycine in mouse cortical homogenates, which was sustained for up to 7 h. Complete cessation of blockade and return to glycine basal levels occurred prior to 24 h, which is in stark contrast to NFPS (>24 h). SSR-504734 potentiated a nearly twofold increase of NMDA receptor-mediated excitatory postsynaptic currents (EPSCs) in rat hippocampal slices and produced an increase in contralateral rotations in mice when microinjected into the striatum. Microdialysis experiments indicated that the inhibitor induced a rapid and sustained increase in extracellular glycine levels in the PFC of freely moving rats [51]. The compound also demonstrated efficacy in a variety of psychosis models [51-53]. SSR-504734 was reportedly in clinical trials for schizophrenia but discontinued after Phase I (data not disclosed) [54]. [Pg.25]

In Equation 12.6 p, is the permanent dipole moment, h is Planck s constant, I the moment of inertia, j the angular momentum quantum number, and M and K the projection of the angular momentum on the electric field vector or axis of symmetry of the molecule, respectively. Obviously if the electric field strength is known, and the j state is reliably identified (this can be done using the Stark shift itself) it is possible to determine the dipole moment precisely. The high sensitivity of the method enables one to measure differences in dipole moments between isotopes and/or between ground and excited vibrational states (and in favorable cases dipole differences between rotational states). Dipole measurements precise to 0.001 D, or better, for moments in the range 0.5-2D are typical (Table 12.1). [Pg.394]

On the basis of these formulae one can convert measurements of area, which equals the integral in the latter formula, under spectral lines into values of coefficients in a selected radial function for electric dipolar moment for a polar diatomic molecular species. Just such an exercise resulted in the formula for that radial function [129] of HCl in formula 82, combining in this case other data for expectation values (0,7 p(v) 0,7) from measurements of the Stark effect as mentioned above. For applications involving these vibration-rotational matrix elements in emission spectra, the Einstein coefficients for spontaneous emission conform to this relation. [Pg.299]

The autput of a mode-locked ruby laser 729) producing a train of pulses of 5 psec duration with a maximum peak power of 5 GW was focused into a cell pressurized with the sample gas. Pulse-energy conversion efficiencies into the Raman lines of up to 70 % have been obtained. The induced rotational lines are broadened this could be due to a strong optical Stark effect 730)... [Pg.47]

As a first example for the application of this technique, we mention the investigation of Stark splitting in molecules studied with a CO2 laser by Brewer etal. The authors shifted the vibration-rotation levels of by an external electric field. With increa-... [Pg.67]

The rotational spectrum of 1,2-dithiin was measured using a pulsed-beam microwave spectrometer in the 8-18 GHz range <1996JSP(180)139> by Stark effect measurements, the electric dipole moment was also determined (/ta = 1.85 D). The molecule proved to be of C2 symmetry with a twisted conformation about the S-S bond and a C-S-S-C dihedral angle of 53.9... [Pg.688]

The rotational quantum numbers of the free linear dipole are j and m (with m S j), and the rotational constant is denoted by B. Analogous to the strong-field limit of the Stark effect, for linear dipoles at small r, one has... [Pg.822]

Pochan, Baldwin and Flygare have analyzed the microwave spectra of cyclopropanone and the isotopic isomers 13Ci, 13C2, and 2,2-dideutero-cyclopropanone.63) The rotational transitions were determined by studying the Stark effect (the shifts and splittings of lines produced by an electric field). The type of transition observed for cyclopropanone was consistent with C v symmetry and the sum of the moments of inertia (/a + /b — Ic) suggested that all four protons are out-of-plane. These data eliminate such structural alternatives as the dipolar oxyallyl tautomer 82 and allene oxide 83. The electric dipole moment (fi ) was calculated to be 2.67 0.10 D, which corresponds to an average of those of acetone (2.93 D) 65> and formaldehyde (2.34D).6 )... [Pg.101]


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See also in sourсe #XX -- [ Pg.218 ]




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