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  • 1
    Electronic Resource
    Electronic Resource
    Angularly resolved vibrational excitation in Na2–He collisions (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 756-763 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report angle-resolved measurements of vi=0 → vf=1 vibrational transitions in Na2–He collisions at an energy of 90 meV. The agreement with calculated cross sections using an ab initio surface is good, both in the angular variation of the cross section as well as with respect to its magnitude relative to the vibrationally elastic process. The calculated (vi=0, ji=0) → (vf=1, jf ) differential cross sections are discussed in some more detail. They show structure, in addition to the rainbow oscillations, related to the fact that the vibrational transition probability vanishes for a specific approach angle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450573
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  • 2
    Electronic Resource
    Electronic Resource
    Rotational rainbow scattering with large Δ j: Energy dependence of the anisotropy of the Na2–Ne, Ar interaction potential (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 2680-2684 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Differential cross sections for rotational transitions in Na2–Ne, Ar collisions are measured up to very large Δj. It is shown that the energy dependent anisotropy ΔR(E) of the interaction potential can be determined from these data using simple classical relations of ΔR and the rainbow angle θR. Excellent agreement with ab initio data is demonstrated and underlines the usefulness of this concept.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452070
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  • 3
    Electronic Resource
    Electronic Resource
    Supernumerary rotational rainbows in Na2–He, Ne, Ar scattering (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 2685-2688 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report the resolution of supernumerary rotational rainbows for rotationally inelastic ji → jf=0 transitions in Na2–He, Ne, Ar scattering. The relation of the angular position of the supernumerary maxima and the anisotropy ΔR of the interaction potential is established. The analysis yields the energy dependent anisotropy ΔR(E) in very good agreement with data from other sources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452071
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  • 4
    Electronic Resource
    Electronic Resource
    Preparation and detection of alignment with high ||m|| selectivity by saturated laser optical pumping in molecular beams (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 286-302 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We describe a technique for preparation of molecules in single ||m|| levels involving saturated laser optical pumping on molecular P, R, and Q transitions. This technique is not limited to small rotational quantum numbers j. It allows the determination of the populations of ||m|| levels for arbitrary distribution functions f ( j,m) or alternatively, the determination of all moments of f ( j,m). In principle, this method is able to completely determine the angular distribution of j vectors. Experimental verification of the high ||m||-state purity achieved in Na2 supersonic beams, as well as of inherent limitations due to hyperfine interaction is provided. For illustration, experimental data on laser-induced alignment, the dependence of the flow induced molecular alignment, and on Δm-propensity rules in differential rotationally inelastic scattering are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451655
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  • 5
    Electronic Resource
    Electronic Resource
    Electrode phenomena and current distribution in a radial multichannel pseudospark switch (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 4180-4184 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microscopic structure and the spatial distribution of the cathode spots in a radial multichannel pseudospark switch have been investigated by means of scanning electron microscopy. Current pulses of about 15 μs duration and peak amplitudes up to 340 kA have been applied. When using stainless steel and copper as electrode material cathode spots of type I and type II are observed. These cathode spots appear in groups (macrospots) with a diameter of several 100 μm. Assuming that the lifetime of the macrospots corresponds to the half period time of the current pulse the distribution of the cathode spots within the macrospots can be explained by a retrograde motion of the spots with a velocity of several 100 m/s in the self-magnetic field of the discharge current. Furthermore, the spatial distribution of the cathode spots within the macrospots can be interpreted by assuming a splitting and a repulsion of the cathode spots. The electrode phenomena show that the discharge current is distributed over a large area which is prerequisite for low erosion and long lifetime operation of the switch. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368633
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  • 6
    Electronic Resource
    Electronic Resource
    Population transfer by stimulated Raman scattering with delayed pulses using spectrally broad light (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 4215-4223 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The feasability of selective and complete population transfer between atomic or molecular levels by stimulated Raman scattering with delayed pulses involving spectrally broad light with characteristics typical for pulsed lasers is investigated. In extension of previous work, the effect on the transfer efficiency of phase fluctuations and of the detuning ΔR of the laser frequencies from the two-photon resonance is analyzed. The minimum pulse energy Pmin required to achieve a transfer efficiency of nearly unity is derived analytically, with some restrictions imposed on the type of phase fluctuations. Pmin increases approximately proportional to the square of the bandwidth of the laser radiation and to the square of ΔR. The conclusions are confirmed by the results of extensive numerical calculations. These studies also reveal a high sensitivity of the transfer efficiency to the autocorrelation of the fluctuating light.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462840
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  • 7
    Electronic Resource
    Electronic Resource
    Vibrationally enhanced inelastic atom–molecule cross sections at very low energies (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 8819-8829 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rate constants for inelastic processes in Na2 (v,j)–Ne, Ar, Na collisions are determined at a mean collision energy of the order of 1 meV in a supersonic seeded beam arrangement. The initial vibrational state v and rotational state j is varied in the range 4≤v≤35 and 5≤j≤25. The Na2 molecules are excited by Franck–Condon pumping near the transition region to free molecular flow and the flux of molecules which survive in the level (v,j) is monitored far downstream behind a small aperture. It is shown that elastic processes do not contribute to the observed signal. The magnitude of the cross section for the sum of all inelastic processes is as large as several hundred A(ring)2. It is found that the vibrational motion of the molecule, which carries an energy of up to 500 meV, strongly influences the collision dynamics. The rate constant increases with v by about 35% within the range of vibrational levels studied here. Some state-to-state rate constants are also reported. The experimental results are in good agreement with data from quasiclassical trajectory calculations on a semiempirical bond-distance-dependent potential surface. The observations can be rationalized by realizing that the long range attraction increases with vibrational excitation since the polarizability of the molecule increases. Furthermore, the vibrational excitation in combination with the relatively long interaction time due to the low collision energy enhances the probability for a change of the initial quantum state of the molecule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462239
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  • 8
    Electronic Resource
    Electronic Resource
    Angularly resolved rotational energy transfer in highly vibrationally excited states: Na2(v=31)–Ne (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 4252-4259 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The scattering of high vibrationally excited sodium molecules Na2(v=31) with Ne atoms at 180 meV collision energy is investigated in a crossed molecular beam arrangement using laser optical methods. Angularly resolved rotationally inelastic and vibrationally elastic cross sections ji→jf are measured for ji =5, 7, and 9≤jf ≤25. Pronounced rotational rainbow maxima are observed, the angular position of which indicates a significantly larger anisotropy of the interaction potential compared to that of Na2(v=0)–Ne. Except for the increase of the anisotropy the vibrational excitation has little effect on the dynamics of rotational energy transfer. Good agreement with a new semiempirical Na2–Ne potential surface V(r,R,γ) is found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460611
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  • 9
    Electronic Resource
    Electronic Resource
    Population transfer between molecular vibrational levels by stimulated Raman scattering with partially overlapping laser fields. A new concept and experimental results (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 5363-5376 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The feasibility of a novel technique for efficient and selective population transfer from a thermally populated level 1 via an intermediate state 2 to level 3 is experimentally demonstrated. It is shown for sodium dimers that the process of on- or near-resonance stimulated Raman scattering with only partially overlapping laser beams is, in particular, useful for the selective population of high vibrational levels of particles in a molecular beam. This is achieved when the interaction with the Stokes laser, coupling levels 2 and 3, begins earlier than the interaction with the pump laser. The phenomenon, which is closely related to the formation of "trapped states,'' is quantitatively explained using the basis of eigenstates of molecules strongly coupled to the radiation fields. The similarity and difference to related techniques such as rapid adiabatic passage phenomena in two-level systems, off-resonant stimulated Raman scattering, or stimulated emission pumping is briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458514
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  • 10
    Electronic Resource
    Electronic Resource
    The effect of vibrational excitation (3≤v‘≤19) on the reaction Na2 (v‘)+Cl→NaCl+Na* (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 9472-9475 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The variation of the total integral cross section for the chemiluminescent channel with the vibrational excitation 3≤v‘≤19 is investigated using laser-induced fluorescence or coherent population transfer, a new method employing delayed interaction with two cw lasers to populate vibrationally excited levels. The cross section increases with v‘ by about 0.76% per vibrational level. The results are in agreement with the results of phase-space calculations, as well as with those from simple curve crossing models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463271
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