Line Stark

There are a number of bands which appear in absorption. Only a few of the transitions are identified. However, it is clear that a nvunber of individual lines (Stark States) can be identified. 

Figure 16. Experimental (circles) and fitted (lines) Stark shifts of four individual pentacene molecules as a function of the applied electrical field [20]. Clearly a quadratic dependence of varying magnitude dominates. In case of molecule C an additional linear term results in an asymmetric behavior and a shifted Stark parabola.

Figure 9.24 Laser Stark spectrum of FNO showing Lamb dips in the components of the line of the ij vibrational transition. (Reproduced, with permission, from Allegrini, M., Johns, J. W. C. and McKellar, A. R. W., J. Molec. Spectrosc., 73, 168, 1978)...

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. 

J. Stark (Greifswald) discovery of the Doppler effect on canal rays and of the splitting of spectral lines in electric fields. 

This is a method which is very attractive in principle and which has been applied to yield approximate barriers for a number of molecules. There are, however, difficulties in its use. In the first place, it is not easy to measure the intensities of microwave lines with accuracy. There are unsolved problems of saturation, reflections in the wave guide, and variation of detector efficiency with frequency which are presumably reponsible for the fact that measurements made with ordinary wave guide spectrometers are not very reproducible. In addition, both the spectral lines may be split into components by tunnelling from one potential minimum to another and this splitting, even though it is not resolved, can alter the apparent intensity. Furthermore, it is often difficult to find pairs of lines such that neither is obscured by Stark lobes from the other. 

Some of these difficulties can be circumvented. In particular a cavity-type Stark effect spectrograph has been built which seems capable of yielding relative intensities of near-by lines to within two or three per cent.32 Barrier values for acetaldehyde and fluoro-ethane have been obtained which are in excellent agreement with those from the frequency method described below. From Eq. (1) it can be seen that the error in v is... 

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). 

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].

One of the simplest examples of line interference is impact broadening of H atom La Stark structure, observed in plasmas [176] (Fig. 4.1.(a)). For a degenerate ground state the impact operator is linear in the S-matrix ... 

Fig.5. Spectra of the Stark effect (solid line), Fig.6. Comparison of the Stark effect spectra the absorption (dotted line), and the first of hetero Y-type, X- and Y-type LB films of... 

Fig.7. Quadratic Stark effect spectrum of a poly(methylmetacrylate) film doped with an azobenzene-linked amphiphile C180AZ0C00H (solid line). Dotted line, broken line, and dash and dotted line show an absorption spectrum of the film, its first derivative, and second derivative, respectively.

Mark s contributions while at the I. G. were not limited to the emerging field of polymer science. In those five years, he also took part in studies of X-ray optics and continued his study of the X-ray structure of metals and metal salts. Other seemingly unrelated paper were published on the width of X-ray emission lines (12), Schlenk isomerism (13), the structure of aromatic compounds (14), and a special "hobby" the optical Stark Effect (15, 16). Regarding this latter work, Mark relates that his supervisors tolerated the research commenting that "as long as they are doing something decent and important" it was okay "as sport doesn t cost much money". 

We have seen that the absorption spectra of (RE) + ions (see Eignres 6.2 and 6.3) consist of several sets of lines corresponding to transitions between the Stark snblevels of 2S+1 j states within the 4f" electronic confignration. A typical absorption spectmm of a (RE) + ion in crystals is like the one sketched in Eignre 6.16. The different sets of transitions correspond to different J J transitions (/ acconnting for the gronnd state), which, in principle, are only permitted at magnetic dipole order the selection rnle is 2 / = 0, 1, with 0 -o- 0 forbidden. 

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. 

Rothem, L., Stark, M., Kaufman, Y., Mayo, L., and Assaraf, Y.G. (2004) Reduced folate carrier gene silencing in multiple antifolate-resistant tumor cell lines is due to a simultaneous loss of function of multiple transcription factors but not promoter methylation. Journal of Biological Chemistry. 279, 374-384. 

In solid state lasers the fluorescence lines are broadened 26) by statistical Stark fields of the thermal vibrating crystal lattice and furthermore by optical inhomogenities of the crystal. The corresponding laser lines are accordinglyjlarge at multimode operation 22)... 

Instead of tuning the laser line, one can also shift the absorption lines across the laser line by Zeeman or Stark effects. This is especially advantageous in the far-infrared region where the tuning range of laser lines is restricted. 

A combination of both methods was realized by Uehara et al. 85,88) They investigated the Stark spectrum of polyatomic molecules in strong electric fields by probing the different Stark components with the Zeeman-tuned laser line. Since the molecular constants of the vibrational ground state are often known from microwave investiga-... 

Fig. 3. Stark modulation spectrum of HDCO around 2850.62 cm", obtained with a Zeeman-tuned Xe laser line at 3.50 fim. The Stark field is perpendicular to the optical field and increases from the bottom towards the top of the figure resulting in an increasing splitting of the Stark levels therefore more and more components are separated. (From Uehara, K.T., Shimizu, T., Shimoda, K., ref. 85))...

By modulating the electric field and using phase-sensitive detection methods, Uehara et al. 8 ) were able to increase the sensitivity considerably and they could even detect Stark splittings of less than the doppler width of the components. Fig. 3 shows the Stark spectrum of HDCO for different electric field strengths. Because of the Stark modulation technique the absorption lines appear differentiated the zero points represent the center of each line. 

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)... 

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