Effect of Velocity-Changing Collisions on the Output of a Gas Laser

Borenstein, Matthew; Lamb, Willis E.

doi:10.1103/physreva.5.1311

Cited by 40 publications

(5 citation statements)

References 7 publications

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“…Some of the discrepancy can be understood to be due to the finite-range effect 9 ; the difference may well be within the range expected for shell effects in highly deformed nuclei. 10 The relative importance of multiple-chance fission contributions to the total fission excitation function calculated with parameter set (c) is exhibited in Fig.…”

mentioning

confidence: 77%

Pulse Fourier-Transform Optical Spectroscopy

1977

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are 12% and 5%, respectively. Some of the discrepancy can be understood to be due to the finite-range effect 9 ; the difference may well be within the range expected for shell effects in highly deformed nuclei. 10 The relative importance of multiple-chance fission contributions to the total fission excitation function calculated with parameter set (c) is exhibited in Fig. 2. The principal multiple-chance fission components are displayed. In the threshold region, multiple-chance fission is dominant; and at 169 MeV, the contributions due to firstthrough fourth-chance fission are 2.5, 1.4, 3.8, and 2.5 mb, respectively. The relative importance of multiple-chance fission decreases with increasing excitation energy, although at 337 MeV the multiple-chance contribution is still 33% of the total.To summarize: (1) It is necessary to fit fission and evaporation-residue excitation functions simultaneously over a broad excitation-energy range and to use experimental Z crtt values in order to obtain unambiguous model parameters.(2) The assumption that only first-chance fission need be considered in such analyses is a poor one for the parametrization considered herein. (3) A reduction in the liquid-drop barriers on the order of 35-45% is necessary to reproduce the experimental excitation functions in the mass-150 region.The optical analog of pulse Fourier-trans form NMR spectroscopy is demonstrated. Doppler-free infrared spectra are obtained for a set of closely spaced 13 CH 3 F transitions at 9.66 jum from two-pulse echo and free-induction decay transients. The effects of elastic or inelastic collisions on the decay rate are obtained for each transition, and the long-range force laws are deduced from the dependence of the scattering cross section on molecular velocity.The method of Fourier transforming transient phenomena from the time to the frequency domain has proven to be an extremely versatile technique in pulsed nuclear-magnetic-resonance (NMR) spectroscopy. 1 With it, ultrahigh-resolution NMR spectroscopy can be performed quickly and with high sensitivity in a set of densely spaced lines. 2 Since the NMR signals display coherent transient behavior, dynamic information about nuclear spin interactions can be derived in a selective manner for each transition as well. 3 This Letter reports an initial demonstration of this Fourier-transform technique in the optical region. By employing suitable coherent optical transient effects in a sample of 13 CH 3 F, we are able to resolve Doppler-free spectra in a set of closely spaced lines (Fig. 1). The decay characteristics for each transition are obtained also and 275

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confidence: 77%

Pulse Fourier-Transform Optical Spectroscopy

1977

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“…The persistence of velocity is defined as 1 (~I)d, = r (, )~l 1&d, e(&~I 2~V l) d Vl (3.14) p 1+ p hl(z2) j (3.15) As is well known [12], and seen here, the parameter ng is associated with the persistence of velocity. We also see that o. , is associated with the persistence of velocity in the exchange process.…”

Section: E Collision Integrals and Integrals Of The Exchange Kernelmentioning

confidence: 96%

Exchange collision kernel

Rogers

Berman

1991

Phys. Rev. A

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In the analysis of laser-spectroscopic line shapes, velocity-changing collisions are accounted for by adding to the density-matrix equations-of-motion terms involving the direct collision kernel. The direct collision kernel is the probability density per unit time that an atom has a specific velocity after a collision, as a function of its velocity before the collision. If the collision partner s velocity distribution is not thermal, however, the direct collision kernel alone does not completely characterize the effect of collisions. In such cases it is necessary to include terms involving the exchange collision kernel. The exchange kernel is the conditional probability density per unit time that the atom has a specific velocity after the collision as a function of its collision partner'8 velocity before the collision. Both the direct and the exchange collision kernels are obtained from the linearized Boltzmann equation. We derive an expression for the exchange kernel in terms of the colliding pair scattering cross section, and calculate the exchange kernel for hard-sphere collisions. Moreover, we propose a phenomenological exchange kernel similar to the Keilson-Storer direct kernel [J. Keilson and K.E.Storer, J. Appl. Ma.th. 10, 243 (1952)] and compare it with the hard-sphere kernel. In an earlier paper [P.R. Berman, J.E.M. Haverkort, and J.P. Woerdman, Phys. Rev. A 34, 4647 (1986)], a connection was made between the collision kerneLs of laser spectroscopy and the collision integrab of classical transport theory. We expand on this earlier work by including the exchange collision kernel, and indicate how results from classical transport theory might be used in setting the parameters appearing in the phenomenological exchange kernel. We interpret an excitation-transfer experiment in terms of the exchange kernel.

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“…To estimate the parameter ε of two colliding parti cles, we used the Keilson-Störer model [27,28]: Here m a and m b are masses of active and buffer mole cules. For HF-Ar this formula gives ε = 0.77.…”

Section: Parameter Of the Collision Hardness εmentioning

confidence: 99%

Near IR TDLS study of the HF first overtone line shape. II. Theoretical analysis

2012

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Results of a theoretical study of the HF first overtone rovibrational absorption spectral line profile (the transition 0-2 R(0)), broadened by Ar (mixture HF : Ar = 1 : 150, T = 295 K, P = 10-300 mm Hg) are presented. The generalized Ciurylo-Pine-Szudy line shape model was selected for the analysis of different factors influencing the spectral line shape. The shortcomings of this model are revealed via validation of its basic assumptions, using the classical trajectory method. Special consideration is given to the elucidation of the nature of the anomalous asymmetry of the HF spectral line shape.

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Effect of Velocity-Changing Collisions on the Output of a Gas Laser

Cited by 40 publications

References 7 publications

Pulse Fourier-Transform Optical Spectroscopy

Pulse Fourier-Transform Optical Spectroscopy

Exchange collision kernel

Near IR TDLS study of the HF first overtone line shape. II. Theoretical analysis

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