Stark effect in quasi-hydrogenic species (original) (raw)
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Observation of the Stark effect in autoionising Rydberg states of molecular hydrogen
Chemical Physics Letters, 1991
The dc Stark effect is studied for autoionising Rydberg states of H 2 converging on the ν +=2 ionisation limit. The levels ( n = 13-22) are excited from the ground state using a coherent XUV source (bandwidth ≈ 1 cm -1) and are strongly perturbed by the field (15-2000 V/cm). Many new states are observed, including the high-/hydrogenic manifolds. A detailed Stark map is obtained for the first time, and a matrix diagonalisation calculation of field-induced state mixing is carried out to explain some of the observed features.
Long-range interactions of hydrogen atoms in excited states. I.<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">mml:mrowmml:mn2mml:miSmml:mo−mml:mn1mml:miSinteractions and Dirac-<mml:math xmlns:mml="http://www....
Physical review, 2017
The theory of the long-range interaction of metastable excited atomic states with ground-state atoms is analyzed. We show that the long-range interaction is essentially modified when quasidegenerate states are available for virtual transitions. A discrepancy in the literature regarding the van der Waals coefficient C6(2S; 1S) describing the interaction of metastable atomic hydrogen (2S state) with a ground-state hydrogen atom is resolved. In the the van der Waals range a0 ≪ R ≪ a0/α, where a0 = /(αmc) is the Bohr radius and α is the fine structure constant, one finds the symmetry-dependent result E2S;1S(R) ≈ (−176.75 ± 27.98) E h (a0/R) 6 (E h denotes the Hartree energy). In the Casimir-Polder range a0/α ≪ R ≪ c/L, where L ≡ E 2S 1/2 − E 2P 1/2 is the Lamb shift energy, one finds E2S;1S(R) ≈ (−121.50 ± 46.61) E h (a0/R) 6. In the the Lamb shift range R ≫ c/L, we find an oscillatory tail with a negligible interaction energy below 10 −36 Hz. Dirac-δ perturbations to the interaction are also evaluated and results are given for all asymptotic distance ranges; these effects describe the hyperfine modification of the interaction, or, expressed differently, the shift of the hydrogen 2S hyperfine frequency due to interactions with neighboring 1S atoms. The 2S hyperfine frequency has recently been measured very accurately in atomic beam experiments.
The Stark effect for the hydrogen atom in a magnetic field
The spectrum of the hydrogen atom in weak perpendicular and parallel electric and magnetic fields is computed and analyzed with allowance for the diamagnetic interaction. In either case the energy spectrum of the highly excited states as a function of the electric field intensity for a fixed magnetic field splits up into three qualitatively different regions. A natural explanation of this effect is found in a quasiclassical analysis of trinomial recursion relations to whose solution both problems can be reduced. The cause of this splitting of the spectrum lies in the restructuring of the states, when the relation between the electric-and magnetic-field intensities is changed, as a result of the appearance or disappearance of effective potential barriers. Those aspects of the quasiclassical approximation for the trinomial recursion relations which are necessary for the analysis of both problems and which have hitherto not been discussed in the literature are considered.
Staggering Effects in Nuclear and Molecular Spectra
Progress in Theoretical Chemistry and Physics, 2002
It is shown that the recently observed ∆J = 2 staggering effect (i.e. the relative displacement of the levels with angular momenta J, J + 4, J + 8, . . . , relatively to the levels with angular momenta J + 2, J + 6, J + 10, . . . ) seen in superdeformed nuclear bands is also occurring in certain electronically excited rotational bands of diatomic molecules (YD, CrD, CrH, CoH), in which it is attributed to interband interactions (bandcrossings). In addition, the ∆J = 1 staggering effect (i.e. the relative displacement of the levels with even angular momentum J with respect to the levels of the same band with odd J) is studied in molecular bands free from ∆J = 2 staggering (i.e. free from interband interactions/bandcrossings). Bands of YD offer evidence for the absence of any ∆J = 1 staggering effect due to the disparity of nuclear masses, while bands of sextet electronic states of CrD demonstrate that ∆J = 1 staggering is a sensitive probe of deviations from rotational behaviour, due in this particular case to the spin-rotation and spin-spin interactions.
The semiclassical resonance spectrum of hydrogen in a constant magnetic field
Nonlinearity, 1996
We present the first purely semiclassical calculation of the resonance spectrum in the diamagnetic Kepler problem (DKP), a hydrogen atom in a constant magnetic field with L z = 0. The classical system is unbound and completely chaotic for a scaled energy ∼ EB −2/3 larger than a critical value c > 0. The quantum mechanical resonances can in semiclassical approximation be expressed as the zeros of the semiclassical zeta function, a product over all the periodic orbits of the underlying classical dynamics. Intermittency originating from the asymptotically separable limit of the potential at large electron-nucleus distance causes divergences in the periodic orbit formula. Using a regularization technique introduced in (Tanner G and Wintgen D 1995 Phys. Rev. Lett. 75 2928) together with a modified cycle expansion, we calculate semiclassical resonances, both position and width, which are in good agreement with quantum mechanical results obtained by the method of complex rotation. The method also provides good estimates for the bound state spectrum obtained here from the classical dynamics of a scattering system. A quasi-Einstein-Brillouin-Keller (QEBK) quantization is derived that allows for a description of the spectrum in terms of approximate quantum numbers and yields the correct asymptotic behaviour of the Rydberg-like series converging towards the different Landau thresholds.
The Stark effect in Rydberg states of a highly polar diatomic molecule: CaF
The Journal of Chemical Physics, 2009
The Stark effect in molecular Rydberg states is qualitatively different from the Stark effect in atomic Rydberg states because of the anisotropy of the ion core and the existence of rotational and vibrational degrees of freedom. These uniquely molecular features cause the electric-field-induced decoupling of the Rydberg electron from the body frame to proceed in several stages in a molecule. Because the transition dipole moment among the same-n * Rydberg states is much larger than the permanent dipole moment of the ion core, the decoupling of the Rydberg electron from the ion core proceeds gradually. In the first stage, analyzed in detail in this paper, ᐉ and N are mixed by the external electric field, while N + is conserved. In the further stages, as the external electric field increases, N + , n * , and v + are expected to undergo mixing. We have characterized these stages in n * = 13, v + = 1 states of CaF. The large permanent dipole moment of CaF + makes CaF qualitatively different from the other molecules in which the Stark effect in Rydberg states has been described ͑H 2 , Na 2 , Li 2 , NO, and H 3 ͒ and makes it an ideal testbed for documenting the competition between the external and CaF + dipole electric fields. We use the weak-field Stark effect to gain access to the lowest-N rotational levels of f, g, and h states and to assign their actual or nominal N + quantum number. Lowest-N rotational levels provide information needed to disentangle the short-range and long-range interactions between the Rydberg electron and the ion core. We diagonalize an effective Hamiltonian matrix to determine the ᐉ-characters of the 3 ഛ ᐉ ഛ 5 core-nonpenetrating 2 ⌺ + states and to characterize their mixing with the core-penetrating states. We conclude that the mixing of the ᐉ =4, N − N + =−4͑g͑−4͒͒ state with lower-ᐉ 2 ⌺ + states is stronger than documented in our previous multichannel quantum defect theory and long-range fits to zero-field spectra.
Zeitschrift f�r Physik D Atoms, Molecules and Clusters, 1987
For deuterium Rydberg atoms in a magnetic field of ...... 6 T we compa re tbe complete experimen tal spectrum io the range-190 em-1 to-20 cm-I with the positions and oscillator strengths of the correspond ing quantum theoretically calculated photoabsorption lines. The agreement is cxccllent. The range of energy covered extends from the end of the I-mixing regime up to tbe regions where tbe approximate integrability of the problem is completely lost, and the corresponding classical system undergoes a transition to chao!>.