Dynamics of interfering wave packets in rubidium by high resolution quantum beat spectroscopy

High resolution quantum beat spectroscopy has been realized to study atomic wave packet dynamics. Wave packets comprising pairs of low quantum number (n = 5 - 8) electronic states were formed in Rb vapor with ultrafast laser pulses, and their dynamics was observed by an all-optical technique of parametric four wave mixing (PFWM). The experimental apparatus designed, constructed and automated for this work provided unprecedented signal intensity that enabled time-frequency-resolved analysis of wave packet dynamics with picosecond temporal resolution over the course of 1100 ps. Both time-resolved and non-time-resolved discrete Fourier methods were applied to measure the concurrent formation of multiple wave packets. Many novel effects and interactions have been measured either for the first time or with greatly improved signal-to-noise ratio. Among them were the formation of the 8S1/2 - 6D5/2 wave packet that was not directly excited by the ultrafast radiation, formation and relative dynamics of quantum beating harmonics up to 73 THz, and quantum beating revivals. The effects of vapor number density and temperature were analyzed experimentally. Interference between the 7S1/2 - 5D5/2 and 8S1/2 - 6D5/2 wave packets (frequencies of 18.225 THz and 10.73 THz, respectively) has been observed for the first time and will be described in detail

LASER SPECTROSCOPY OF THE PHOTOASSOCIATION OF Rb-Ar AND Rb-Kr THERMAL PAIRS: STRUCTURE OF THE Rb-RARE GAS A2_1/2 STATE NEAR THE CLASSICAL LIMIT

A new laser spectroscopic technique has been demonstrated for examining the structure of alkali--rare gas diatomic electronic states near the classical limit. In two-color experiments, Rb--Ar or Rb--Kr thermal pairs are excited by free$leftarrow$free or bound$leftarrow$free transitions while monitoring the amplified spontaneous emission produced on the Rb D$_1$ or D$_2$ lines. Spectra observed lying within 10 cm$^{-1}$ of the separated atom limit for the A$^{2}Pi_{1/2}$ states of Rb--Ar and Rb--Kr will be presented and discussed

OBSERVATION OF QUANTUM BEATING IN Rb AT 2.1 THz AND 18.2 THz: LONG-RANGE Rb*-Rb INTERACTIONS.

begin{wrapfigure}{r}{0pt}_x000d_ includegraphics[scale=.6]{fig.eps}_x000d_ end{wrapfigure}_x000d_ The interaction of Rb 7s $^{2}S_{1/2}$, 5d $^{2}D_{3/2,5/2}$ and 5p $^{2}P_{3/2}$ atoms with the background species at long range (100-1000AA) has been observed by pump-probe ultrafast laser spectroscopy. Parametric four-wave mixing in Rb vapor with pairs of 50-70 fs pulses produces coherent Rb 6P-5S emission at 420 nm that is modulated by Rb quantum beating. The two dominant beating frequencies are 18.2 THz and 2.07 THz, corresponding to quantum beating between 7S and 5D states and to the (5D-5P$_{3/2}$)-(5P$_{3/2}$-5S) defect, respectively. Analysis of Rabi oscillations in these pump-probe experiments allows for the mean interaction energy at long range to be determined. _x000d_ The figure shows Fourier transform spectra of representative Rabi oscillation waveforms. The waveform and spectrum at left illustrate quantum beating in Rb at 2.1 THz. The spectrum at right is dominated by the 18.2 THz frequency component generated by 7S-5D beating in Rb. Insets show respective temporal behaviors of the 6P-5S line near the coherent transient (zero interpulse delay)._x000d_ _x000d