Total Scattering Cross Section for Na on He Measured by Stimulated Photon Echoes

Abstract

or holes broken (A6 = 0 for J^ = i"), so that our data should lie on a straight line. (The results deduced from our tables are consistent with these predictions.) Finally, let us note that these pseudo mirror pairs all satisfy the relations •within a few percent. This is an enlargement of the so-called De Shalit relation {gs''gi)p/(gs -gi)n = -1-20 deduced in the frame of the extreme single-particle model. ^See, for example, R. G. Sachs, Phys. Rev. ^, 611 (1946).A technique which employs heretofore unappreciated aspects of the optical stimulated echo was developed and used to measure the total scattering cross section for Na(3Siy5)-He and Na(3Pi/2)-He collisions. The repulsive-core-dominated Na(3Si/2)-He collision is found to be relatively soft. The cross section for degradation of the 3Siy5-3Pi/2 superposition, determined from photon-echo-dec ay measurements, is anomalous in that it is smaller than the total elastic-so altering cross section with Na in either state separately.The study of atomic scattering, traditionally carried out by atomic-beam measurements/ has recently been supplemented by laser techniques.^ In this Letter we report the first application of a coherent-transient laser technique to the study of velocity-changing collisions (VCC) in an atomic system.^ CXir technique utilizes unappreciated novel aspects of the three-pulse stimulated photon echo^ (SP echo) to provide relatively direct measurements of VCC. We predict and demonstrate experimentally (e.g., Fig. 1) that phase memory information stored in either the ground ^^^ •^' O^scilloscope trace showing scattered light from three excitation pulses (third row of the table in Fig. 3 with K'-^/|K'[ = -1) and the subsequent SP echo (fourth pulse) pronounced on the SS-SP1/2 transition of Na when the second-to-third pulse separation is = 17 times the 16-nsec lifetime of the SP^/z state. At the time of the third pulse a negligible ^ 10"^ of the intially excited population remains in the ^P^^ state. The echo persists because of the information stored in the ground state alone. (Horizontal: 50 nsec/div.)

The dynamics of one-dimensional excitons in liquids

“…In that case dephasing on one transition can be nullified by rephasing on another one. This correlation was demonstrated some time ago for the inhomogeneous widths of optical transitions in gas-phase 53 and low-temperature solid 54 multilevel systems. For liquids, where there is no proper ͑static͒ inhomogeneous width, but rather frequency fluctuations on multiple time scales, this correlation between fluctuations of optical transitions in multilevel systems is not as well established.…”

Transient four-wave mixing and coherent transient optical phenomena

“…4 • 5 The effect is more significant for longer time separations between·pulses, and has already been experimentally demonstrated. 15 For sufficiently short pulse separation, the effect is negligible.…”

A solid-state light–matter interface at the single-photon level

“…However, due to the periodic structure of the absorption profile, the collective state will be re-established after a pre-programmed time 2π/∆, where ∆ is the period of the spectral grating. This leads to a coherent photon-echo type re-emission in the forward spatial mode [11,25,26,27]. Note that in our experiment the light field is stored as a collective excitation on the optical transition, contrary to all previous experiments at the single photon level, where collective excitations of spin states were used [5,6,7].…”

“…The mapping is done by coherently absorbing the light in an ensemble of inhomogeneously broadened atoms spectrally prepared with a periodic modulation of the absorption profile [11,25,26,27]. The reversible absorption by such a spectral grating is at the heart of the recently proposed multimode quantum memory scheme based on AFC [11].…”