Stark levels

Polik W F, Guyer D R and Moore C B 1990 Stark level-crossing spectroscopy of Sq formaldehyde eigenstates at the dissociation threshold J. Chem. Phys. 92 3453-70... 

Thus, the excited state " Gs/2 (or splits into three Stark levels in Dj symmetry, labeled by 1/2, 1/2. and 3/2. while the terminal state //9/2 (or splits into live Stark levels, 1/2, 1/2, 1/2, 3/2, and E-ij2. In fact, the five peaks observed in the emission spectrum of Figure 7.9 are related to these five terminal levels. This is because, at the low temperature (10 K) of the spectrum, radiative transitions only depart from the lowest level of the excited state. 

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))...

Fig. 6.10 Calculated SFI profile for diabatic ionization of the H like m a 3 states. Top, extreme members of the n = 31, m = 3 Stark manifold. The crosses represent the points at which each m a 3 Stark state achieves an ionization rate of 10 s I. Bottom, calculated SFI profile for diabatic ionization of a mixture containing equal numbers of atoms in each m a 3 Stark level for n = 31 at a slew rate of 109 V/cm s. (from ref. 26).

Fig. 6.13 Part of the excitation spectrum oftheNaw = 29 Stark levels from the 3d state in an electrostatic field of 20.5 V/cm corresponding to nj values of n — 3, n — 4, and n — 5. The energy splitting between m = 0 (highest energy fine in the doublets) and m = 1 states is of the order of 180 MHz. The arrows indicate theoretical positions of energy levels obtained by a numerical diagonalization of the Stark Hamiltonian (from ref. 28).

Fig. 7.2 Energy levels of the H n = 15, m = 0 Stark levels. The broadening of the levels corresponds to an ionization rate of 106 s-1. The extreme red and blue state ionization rates are taken from the calculations of Bailey et al. (ref. 5), and those of the intermediate states...

Fig. 7.6 Two Stark levels with an avoided crossing a 0. If the field is slewed through the avoided crossing in a time long compared to l/cu0 the passage is adiabatic (solid arrow), while if it is slewed rapidly through the crossing the passage is diabatic (broken arrow).

In alkali atom experiments no explicit resonances have been observed in microwave ionization. However, there are indirect confirmations of the multiphoton resonance picture. First, according to the multiphoton picture the sidebands of the extreme n and n + 1 Stark levels should overlap if E = 1/3n5. In the laser excitation spectrum of Na Rydberg states from the 3p3/2 state in the presence of a 15 GHz microwave field van Linden van den Heuvell et al. observed sidebands spaced by 15.4 GHz, as shown in Fig. 10.15.18 The extent of the sidebands increases linearly with the microwave field, as shown in Fig. 10.15, and the n = 25 and n = 26 sidebands overlap at microwave fields of 150 V/cm or higher, matching the observation that the 25d state has an ionization threshold of 150 V/cm in a 15 GHz field. 

Recently, we also observed an anomalous thermalization phenomenon in Er Gd203 (1 at%) nanocrystals with diameters of 40-50 nm. In the excitation spectra at 2.9 K, hot bands originating from the upper stark level of 4Ii5/2 (38 cm-1) were observed. These hot bands disappear when temperature goes up to 5 K. Our preliminary results show that the anomalous thermalization phenomena in this system are more complicated, because they depend on the laser power and temperature. The effect of laser heating or temperature fluctuation in nanocrystals must be ruled out before a definite conclusion can be reached. 

Derivation of Phase-Integral Formulas for Profiles, Energies and Half-Widths of Stark Levels... 

In the present chapter we shall start from the results obtained in Chapter 3 and treat the Stark effect of a hydrogenic atom or ion with the use of the phase-integral approximation generated from an unspecified base function developed by the present authors and briefly described in Chapter 4 of this book. Phase-integral formulas for profiles, energies and half-widths of Stark levels are obtained. The profile has a Lorentzian shape when the level is narrow but a non-Lorentzian shape when the level is broad. A formula for the half-width is derived on the assumption that the level is not too broad. 

As already mentioned, we define the positions of the Stark levels as the energies for which (OJ/QJ )2 assumes its maxima for fixed F, m and n. When the energy dependence of the //-dependent quantities in (5.17b) is much smaller than that of tanv, it is seen that the resonances, i.e., the minima of (fT /Q )2, occur when approximately... 

We shall next give an explicit formula for the half-width T on the energy scale of a not too broad Stark level. To this purpose we write (5.17b) with the use of the approximate version of (5.18a) as u +1... 

For a not too broad Stark level an adequate approximate formula for T is obtained when one neglects the change with energy of u over the width of the level. Thus one finds from (5.51) that (Q /Q")2 assumes half of its maximum value when... 

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