Coherence resonance in the alignment of Hg 201 atoms by the 2537-Å line

L. N. Novikov, I. Popesku

C. J. K. Quayle, I. M. Bell, Endre Takács +3 more

We have measured the alignment of the photofragments produced by photodissociation of Hg–Ar van der Waals molecules using light around 253.7 nm. The molecules are produced in the X0+ ground state in a supersonic expansion. Tunable laser light close to the Hg 6 1S0–6 3P1 transition is then used to excite the molecule to the B1± state, in which it dissociates. The alignment of the resulting Hg(3P1) asymptotic atoms is probed by tuning a delayed second laser to the 435.8 nm Hg 6 3P1–7 3S1 atomic transition and monitoring the subsequent fluorescence on the 7 3S1–6 3P2 transition around 546.1 nm. These measurements have been made, we believe for the first time, as a function of dissociating energy from very close to threshold to higher energies. The alignment shows a significant rise with increasing photon energy in line with a semiclassical picture of orbital locking at lower energies and rapid decoupling at higher energies. The results exhibit good agreement with the results of a fully quantum mechanical theory of the system.

I. M. Bell, C. J. K. Quayle, Keith R. Burnett +1 more

We have measured the alignment of Hg(6 $^{3}$${\mathit{P}}_{1}$) atoms following off-resonant excitation of the Hg 6 $^{1}\mathrm{S}_{0}$--6 $^{3}\mathrm{P}_{1}$ transition in the presence of Kr. We present a polarization spectrum for both red and blue wings out to detunings beyond 100 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. This represents a considerable extension to the existing results, which has been made possible by the use of a pump-and-probe excitation scheme. In the experiment a pulsed laser, detuned from the resonance, creates an alignment in the upper state. This is probed by tuning a delayed second laser to a higher transition and monitoring laser-induced fluorescence from the two-step process. The alignment of the asymptotic Hg(6 $^{3}$${\mathit{P}}_{1}$) atoms is determined by comparison of the signals obtained for different relative polarizations of the lasers. We discuss the advantages of this method and the relation of the raw data to the polarizations presented. The results are discussed within the context of a simple quasiclassical model of the process.

Mark G. Raizen, F. Elsner, Jonas Bergquist +2 more

Bernard Cheron, G. Cremer, D. Lecler +1 more

The excitation and alignment transfer resulting from the non-resonant second kind collision : Hg(6 1P1) + Cd(5 1S 0) → Hg(6 1S0) + Cd(6 3S 1) + 0.32 eV, at thermal velocity, has been studied by means of the Hanle effect. The alignment transfer rate was found to be α(2) = - 0.20 ± 0.05 .

Wayne M. Itano, Jonas Bergquist, Randall G. Hulet +1 more