Deflection recoil

Figure 3-3.22 Negative ion recoil spectrum for oxygen recoiled from a Ni surface by 2keV Ne projectile. The peak labelled R is a direct recoil, and the other two peaks labeled DR are deflected recoils [10]. The solid line is drawn to guide the eye.

To complete the explanation of why GP effects cancel in the ICS, we need to explain why the 2-TS paths scatter into negative deflection angles. (It is well known that the 1-TS paths scatter into positive deflection angles via a direct recoil mechanism [55, 56].) We can explain this by following classical trajectories, which gives us the opportunity to illustrate a further useful consequence of the theory of Section II. 

Another method, based on an old idea about radiation pressure, uses the local separation of different isotopes in atomic or molecular beams. If the laser beam which crosses the molecular beam at right angles is tuned to an absorption line of a defined isotope in a molecular beam containing an isotopic mixture, the recoil from the absorption of the laser photons results in a small additional transverse velocity component. This leads to a beam deflection for the absorbing molecules which enables the desired isotope to be collected in a separate collector 154g)... 

For the reactions K + HBr and K + DBr, the KBr recoil energy distribution has been determined in a crossed-molecular beam experiment using a mechanical velocity selector. No difference was found in the form of the translational energy distributions for the two reactions for which a value of 0.30 may be derived. Although all the angular momentum appears in the product rotation, the moments of inertia for the alkali halides are large, which implies that the mean product rotational energy is quite small ( 0.21, 0.21 and 0.09 for K, Rb, Cs + HBr, respectively [3] these values are derived from the rotational temperatures obtained by electric deflection analysis). 

An instrument for comparative determinations of the performance of different explosives. A mortar, provided with a borehole, into which a snugly fitting solid steel projectile has been inserted, is suspended at the end of a 10 It long pendulum rod. Ten grams of the explosive to be tested are detonated in the combustion chamber. The projectile is driven out of the mortar by the fumes, and the recoil of the mortar is a measure of the energy of the projectile the magnitude determined is the deflection of the pendulum. This deflection, which is also known as... 

Gillen et al. [67] estimated the distribution of c.m. recoil energies from the velocity analysis. No significant differences were observed in scattering from K + HBr and from K + DBr, and E mp was approximately 1.5 kcal/mole (0.06 eV). Electric deflection analysis [34, 35] on MBr from K (and Cs) + HBr indicates that (IFr ot) = 1.5 kcal/mole (0.06 eV) and confirms that the rotational momentum of KBr is approximately equal to the orbital momentum of the reactive collisions [see equation (43)]. These measurements suggest that a considerable fraction of the small amount of energy available in this reaction enters the KBr vibration. 

Instead of measuring the transmission of electrons one can measure the transmission of the target particles in a crossed-beam experiment, where a beam of electrons intersects a beam of target particles (Bederson, 1968). The recoil imparted to the target atom or molecule deflects it out of the original beam and the decreased beam intensity is a measure of the total cross section. Usually one uses a d.c. molecular beam and a modulated electron beam and associated phase-sensitive detection of the transmitted molecular beam. If the two beams are rectangular with a common dimension h, then (Bederson, 1968)... 

An interesting application of atomic deflection by photon recoil is the collimation and focusing of atomic beams with lasers [1138]. Assume atoms with the velocity u = 0, pass through a laser resonator, where an intense standing op-... 

Fig. 9.13 Cooling, deflection and compression of atoms by photon recoil. The electro-optic modulators (EOM) and the acousto-optic modulator (AOM) serve for sideband generation and frequency tuning of the cooling laser sideband [1136]...

Another application is the deflection of atoms by photon recoil. For sufficiently good beam collimation, the deflection from single photons can be detected. The distribution of the transverse-velocity components contains information about the statistics of photon absorption [1207]. Such experiments have successfully demonstrated the antibunching characteristics of photon absorption [1208]. The photon statistic is directly manifest in the momentum distribution of the deflected atoms [1209]. Optical collimation by radial recoil can considerably decrease the divergence of atomic beams and thus the beam intensity. This allows experiments in crossed beams that could not be performed before because of a lack of intensity. 

One example of an application is the measurement of the gravitational acceleration g on earth with an accuracy of 3 x 10 g with a light-pulse atomic interferometer [1291]. Laser-cooled wave packets of sodium atoms in an atomic fountain (Sect. 9.1.9) are irradiated by a sequence of three light pulses with properly chosen intensities. The first pulse is chosen as 7r/2-pulse, which creates a superposition of two atomic states 1) and 2) and results in a splitting of the atomic fountain beam at position 1 in Fig. 9.71 into two beams because of photon recoil. The second pulse is a tt-pulse, which deflects the two partial beams into opposite directions the third pulse finally is again a tt/2-pulse, which recombines the two partial beams and causes the wave packets to interfere. This interference can, for example, be detected by the fluorescence of atoms in the upper state 2). 

It should be emphasized that the absorption coefficient is a much more restricted concept than the attenuation coefficient. Attenuation also includes the purely elastic process in which the photon is merely deflected and does not give up any of its initial energy to the absorber. In a photoelectric interaction, the entire energy of the incident photon is absorbed by an atom of the medium, while in the Compton effect, some energy is absorbed and appears in the medium as the kinetic energy of a Compton recoil electron the balance of the incident energy is not absorbed and is present as a Compton scattered photon. 

The photon recoil can be used not only for the deceleration of collimated atomic beams but also for the deflection of the atoms, if the laser beam... 

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