The radio-frequency electric resonance technique—a tool for investigating ion-atom collisions

The rf electric resonance technique is discussed with special regard to its applicability to the analysis of excitation processes in ion-atom collisions. In particular, it is useful for investigating substate populations of excited Helium atoms and other He-like systems. A convenient set-up for the rf resonance circuit and interaction region is described. Within the frequency range 100 MHz?ν?1000 MHz, rf electric fieldsE ₁?100 V/cm were applied to He atoms excited by ion impact.E ₁ can accurately be measured using level-crossing techniques, and thus a detailed analysis of the shapes and amplitudes of resonance signals becomes possible.     

Untersuchungen zum Stark-Effekt metastabiler Terme im Ba I-Spektrum durch Nachweis von Hochfrequenzübergängen

By detection of r.f.-transitions between Zeeman-sublevels the Zeeman-splitting of the metastable 6s 5d-levels and of the 6s 6p³ P ₁-level of the even Ba-isotopes was investigated under the influence of an electric field in addition to a magnetic field. From the measurements the following tensor polarizabilities were deduced: α_ten(³D₃)=?29(5) kHz/(kV/cm)², α_ten(³ D ₂)=?13(3) kHz/(kV/cm)², α_ten(³D₁)=?10(2) kHz/(kV/cm)², α_ten(¹ D ₂)=?16(3) kHz/(kV/cm)². No effect due to electric fields up to 50 kV/cm was observed in the Zeeman-splitting of the 6s 6p ³ P ₁-level. Therefore the tensor polarizability of the 6s 6p³P₁-level must be much smaller than those of the 6s 5d-levels. The results will be discussed by considering the oscillator strengths both of the infrared transitions between the two multiplets 6s 5d ³ D and 6s 6p ³ P and of transitions to other low lying levels.     

Cascade-free lifetime measurements on the 1s3d-levels of He I

He-atoms have been excited using 35 keV-He⁺-ion-He-atom-collisions. Investigating the electric and magnetic depolarization of fluorescence light, cascade-free lifetime measurements on the 1s 3d ¹ D and³ D-levels of He I have been performed. From our measurements we deduced:τ(3¹ D)=(15.3±0.3)ns,τ(3³ D)=(14.2±0.6)ns.     

Full counting statistics of strongly non-ohmic transport through single molecules

We study analytically the full counting statistics of charge transport through single molecules, strongly coupled to a weakly damped vibrational mode. The specifics of transport in this regime--a hierarchical sequence of avalanches of transferred charges, interrupted by "quiet" periods--make the counting statistics strongly non-Gaussian. We support our findings for the counting statistics as well as for the frequency-dependent noise power by numerical simulations, finding excellent agreement.