Stark resonance

Fig. 8.15 (a) Experimental photionization spectrum from the Na 1 3/2 state in a field E = 3.59 kV/cm, vs photon energy hw, within 0.01 eV of threshold (from ref. 21). Both the laser populating the 3p3/2 state and the second scanned laser are polarized parallel to the static field. Note labeling of Stark resonances (n,/ ) for m = 0 and 1. (b) Theoretical cross section, from the density of states theory. Both m = 0 and 1 final states are present (from... 

The quasistationary nature of the Stark resonances, due to the fact that the energy eigenvalue spectrum of one of the coupled differential... 

The CESE method is applicable directly. Nicolaides and Themelis (49) considering the asymptotic behaviour of the LoSurdo-Stark resonance states, showed that the wave function is regul2irizable by the complex rotation transformation and that the complex energy of the resonance can be obtained as a solution of the CESE. In the case of a magnetic field, the asymptotic behaviour of the resonance wave function is governed by the atom potential, hence the results for field-free atoms (26) remain valid. 

The results for 0,0,n — 1) Stark resonances are presented in Figures 1 and 2, where the curve n = 00 corresponds to the initial term of the 1/n-expansion. Note that in very strong fields. Stark shifts change their sign. For further details, we refer the reader to [4-6]. 

With the sub-Doppler resolution of the Lamb-dip technique, about 500 Stark resonances have been identified for 44 lines of the V2 band and 31 lines of the V4 band [13]. Two Doppler-free lines with signs opposite to those of Lamb dips were observed in a study of the V2 °P(5,3) transition by laser Stark spectroscopy using the 10P(18) CO2 laser line. They were identified as infrared-infrared double resonance transitions, caused by accidental overlapping of the °P(5,3) line in the V2 band with the °P(4,3) line in the hot band 2V2-V2 [14 to 16]. 

In these experiments L4] we observed narrowing of broad mi, = 0 spectral features by a factor of more than 100 (limited only by the 700 MHz resolution of the laser). Fig. 1 shows theoretical and experimental spectra of a particular Stark resonance at various fields in... 

FIG. 2. Calculated ionization widths for various Stark resonances. The peaks and valleys from interferences have been smoothed out for clarity only their residuals remain as bumps in the plateau areas. 

Marshaii M D, Charo A, Leung H O and Kiemperer W 1985 Characterization of the iowest-iying n bending state of Ar-HCi by far infrared iaser-Stark spectroscopy and moieouiar beam eiectric resonance J. Chem. Phys. 83 4924-33... 

Laser Stark (or laser electronic resonance) spectroscopy... 

D. D. Stark and W. G. Bradly, Magnetic Resonance Imaging Mosby, Lanham, Md., 1988. 

Perhaps the first clear observation of a reactive resonance in a collision experiment was recently made for the F + HD —> HF + D reaction.65-67 This reaction was one isotopomer of the F + H2 system studied in the landmark molecular beam experiments of Lee and co-workers in 1985.58 Unlike the F + H2 case, no anomalous forward peaking of the product states was reported, and results for F + HD were described as the most classical-like of the isotopes considered. Furthermore, a detailed quantum mechanical study68 of F + HD —> HF + D reaction on the accurate Stark-Werner (SW)-PES69 failed to locate resonance states. Therefore, it was surprising that the unmistakable resonance fingerprints emerged so clearly upon re-examination of this reaction. 

From a study of the microwave spectrum of 2-methylselenophene, the second-order Stark effect in the ground state was determined.11 The technique used was double radiofrequency-microwave resonance. For the identification by the double resonance method transitions of chiefly the A-state were chosen. From these observations the components of the dipole moment of 2-methylselenophene and the total dipole moment were determined. 

Josephson L, Lewis J, Jacobs P, Hahn PF, Stark DD (1988) The effects of iron oxides on proton relaxivity. Magn Reson Imaging 6(6) 647-653... 

With this procedure, as with the double-resonance methods in atomic physics, Zeeman and Stark splittings, hyperfine structures and A doublings in molecules can be measured with high precision, even if the observed level splittings are far less than the optical dopp-ler width. From the width of the rf resonance and from the time response of the pumped systems, orientation relaxation rates can be evaluated for individual v J") levels. Other possible applications of this promising technique have been outlined by Zare 30) Experiments to test some of these proposals are currently under investigation and their results will be reported elsewhere. 

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