Beam Of Neon Atoms Research Articles

1932, a watershed year in nuclear physics

The consequences, for good and ill, of that annus mirabilis of discovery and invention are still very much with us.

The infrared spectrum of HOOH+ trapped in solid neon

When a Ne:H(2)O(2) mixture is codeposited at 4.3 K with a beam of neon atoms that have been excited in a microwave discharge, three new, photosensitive absorptions appear which can be assigned to the three infrared-active vibrational fundamentals of trans-HOOH(+). When the Ne:H(2)O(2) deposition system is pretreated with the vapors of D(2)O, the product absorptions include new peaks which can be attributed to vibrational fundamentals of trans-HOOD(+) and trans-DOOD(+). Density functional calculations of the vibrational fundamentals of the three hydrogen peroxide cation isotopologues support the proposed assignments. Broad, photosensitive product absorptions also appear near the positions of vibrational transitions of O(3)(-), and may be contributed by a weakly bound complex of that species with H(2)O.

The infrared spectra of BF3+ and BF2OH+ trapped in solid neon

Observations on a Ne:BF(3) = 400:1 mixture into which a trace of normal or isotopically enriched water had been introduced, codeposited at 4.3 K with a beam of neon atoms that had been excited in a microwave discharge, demonstrate that a pair of absorptions at 1662 cm(-1) and 1722 cm(-1) that were previously assigned to the two boron-isotopic species of BF(3)(+) should be reassigned to a BF(2) stretching fundamental of BF(2)OH(+). The OH stretching fundamental of that product was identified for the first time at 3240 cm(-1). The degenerate BF(3) stretching fundamental of (11)BF(3)(+) appears at an unusually high frequency, 1790 cm(-1), consistent with strong pseudo-Jahn-Teller interaction of that ground-state fundamental with the B̃(2)E(') electronic state, as predicted by theory. The recent availability of detailed ab initio and density functional calculations of the vibrational fundamentals of BF(2)(-) and BF(3)(-) facilitates assignment of the infrared absorptions of those two products.

The infrared spectra of C2H4+ and C2H3 trapped in solid neon

When a mixture of ethylene in a large excess of neon is codeposited at 4.3 K with a beam of neon atoms that have been excited in a microwave discharge, two groups of product absorptions appear in the infrared spectrum of the deposit. Similar studies using C(2)H(4)-1-(13)C and C(2)D(4) aid in product identification. The first group of absorptions arises from a cation product which possesses two identical carbon atoms, giving the first infrared identification of two fundamentals of C(2)H(4)(+) and three of C(2)D(4)(+), as well as a tentative identification of ν(9) of C(2)H(4)(+). The positions of these absorptions are consistent with the results of density functional calculations and of earlier photoelectron studies. All of the members of the second group of product absorptions possess two inequivalent carbon atoms. They are assigned to the vinyl radical, C(2)H(3), and to C(2)D(3), in agreement with other recent infrared assignments for those species.

A hexapole magnetic guide for neutral atomic beams

In this paper we present a multiple element magnetic device to guide atoms using a spatially inhomogeneous magnetic field formed by a series of permanent hexapole magnets. The operation of the device is demonstrated using an enhanced beam of neon atoms in the 3P2 metastable state. These atoms are guided around a bend of 30 degrees from their original path. A flux of 4.35 x 10(9) +/- 2 x 10(7) atoms s(-1) was measured after the device yielding a transmission efficiency of approximately 9% of the input flux. Simulations of the center of mass motion of the atoms through the magnetic guide have been performed giving reasonable agreement with the experimental results.

Advances in Electromagnetic Launch Science and Technology and Its Applications

The U.S. continues a broad spectrum of research to provide the scientific underpinnings for electromagnetic launch. These efforts include fundamental research on materials, properties of materials subjected to electromagnetic and thermal stresses, railguns (particularly the rail-armature sliding interface), coilguns, and energy storage and power conditioning. There is also broad and growing interest in novel applications of electromagnetic launch. For example, a supersonic beam of neon atoms have been slowed and stopped, opening the door for investigating the atomic and molecular properties of most of the periodic table of atoms and certain molecules. Research is continuing on magnetic brakes and the more traditional research on the launch of materials to hypervelocities. More recently, the launching of materials into the Earth's orbit or even deeper in space is obtaining renewed interest. Consequently, some attention is being given to the types of materials of projectiles for hypersonic flight. The U.S. Navy has initiated new multidisciplinary university research teams including physics, chemistry, and materials science to develop new diagnostic tools and to provide a more detailed examination of the rail-armature interface. Most significantly, the U.S. Army has elevated its emphasis from electromagnetic launch science and technology development to the operational consequences of long-range precision fires. In concert with the recent U.S. Navy efforts on long-range fires, it is anticipated that the pull of these applications will enable even greater advances in the science and technology of electromagnetic launch.

Infrared spectra of ClCN+, ClNC+, and BrCN+ trapped in solid neon

When a mixture of ClCN or BrCN with a large excess of neon is codeposited at 4.3 K with a beam of neon atoms that have been excited in a microwave discharge, the infrared spectrum of the resulting solid includes prominent absorptions of the uncharged isocyanide, ClNC or BrNC, and of the corresponding cation, ClCN+ or BrCN+. The NC-stretching fundamentals of the isocyanides trapped in solid neon lie close to the positions for their previously reported argon-matrix counterparts. The CN-stretching absorptions of ClCN+ and BrCN+ and the CCl-stretching absorption of ClCN+ appear very close to the gas-phase band centers. Absorptions of two overtones and one combination band of ClCN+ are identified. Reversible photoisomerization of ClCN+ to ClNC+ occurs. The two stretching vibrational fundamentals and several infrared and near infrared absorptions associated with electronic transitions of ClNC+ are observed. Minor infrared peaks are attributed to the vibrational fundamental absorptions of the CX and CX(+) species (X=Cl,Br).

Infrared spectra of NH2NO, NH2NO+, and NNOH+ and of the N2⋯H2O complex trapped in solid neon

When a Ne:H2:N2O mixture is co-deposited at 4.3 K with a beam of neon atoms that have been excited in a microwave discharge, NH2NO+ is stabilized in sufficient concentration for detection of five of its vibrational fundamentals. Their assignments are supported by isotopic substitution studies and by the results of unrestricted B3LYP/cc-pVTZ calculations. Electron recombination results in the stabilization of NH2NO, for which the previously reported argon-matrix assignments are confirmed and extended. The OH-stretching fundamental of NNOH+ also is present in the spectrum of the initial sample deposit, but because of proton sharing with the neon matrix is shifted 43.3 cm(-1) from the gas-phase band center. The OD-stretching fundamental of NNOD+ is identified for the first time in the present study. An absorption at 2311.1 cm(-1) is contributed by the NN-stretching vibration of a complex of N2, probably with an ionic species. On prolonged visible and near-ultraviolet irradiation of the deposit, absorptions of the binary N2...H2O complex become increasingly prominent.

Reflection-type hologram for atoms.

A cold metastable neon atomic beam was manipulated with a reflective amplitude hologram that was encoded on a silicon surface. A black-and-white pattern of atoms was reconstructed on a microchannel plate detector. The hologram used the enhanced quantum reflection developed by authors and was made of a two-dimensional array of rectangular low and high reflective cells. The surface of the high reflective cell was composed of regularly spaced roof-shaped ridges, while the low reflective cell was simply a flat surface. The hologram was the first demonstration of reflective atom-optical elements that used universal interaction between a neutral atom and solid surface.

The infrared spectra of OCS+ and OCS− trapped in solid neon

When a Ne:OCS sample was codeposited at approximately 5 K with a beam of neon atoms that were excited in a microwave discharge, the infrared spectrum of the resulting deposit included absorptions which can be assigned to OCS+, OCS−, and one or more dimer ions. Detailed isotopic substitution studies support the assignments offered for OCS+ and OCS−. The CO- and CS-stretching absorptions observed for OCS+ isolated in a neon matrix lie close to the corresponding gas-phase band centers. The CO- and CS-stretching fundamentals of OCS− isolated in solid neon were observed for the first time at 1646.4 and 718.2 cm−1, respectively. These frequencies are in good agreement with values previously calculated using ab initio and density functional methods. The least-squares force constant fit to the data obtained in isotopic substitution experiments supports the proposed assignment. Dimer ions were also stabilized, but infrared data for these species were insufficient to provide definitive assignments.

Real time interferometric manipulation of a neutral atomic beam by electric field

Electric-field-controlled holography for atoms is demonstrated. Platinum electrodes are deposited among the array of parallel slits that are made on a silicon nitride film. A cold neon atomic beam in the 1s3[2p5(2Po1/2)3s : J = 0] metastable state is sent through the film and form a Fraunhofer diffraction pattern on a microchannel plate detector that is placed in the downstream of the film. By controlling the potential of each electrode an arbitrary one-dimensional diffraction pattern of atoms has been generated.PACS No. 78.90

Imaging of an atomic beam with electrostatic lenses

The imaging of a neutral atomic beam by electrostatic force has been demonstrated. An ultracold neon atomic beam in the ${1s}_{3}[{(2p)}^{5}{3s:}^{1}{P}_{0}]$ state illuminated a transparent object, passed through a set of three electrostatic lenses, and formed the image on a microchannel plate detector with the magnification of unity. Each lens consisted of two parallel cylinders that functioned as a concave lens along one axis and as a convex lens along the other axis. The atomic polarizability of neon in the ${1s}_{3}$ state has been also determined to be $2.8(\ifmmode\pm\else\textpm\fi{}0.1)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}39} {\mathrm{Fm}}^{2}.$

Matrix isolation study of the interaction of excited neon atoms with CCl4: Infrared spectra of the ion products and of Cl2CCl⋅⋅Cl

When a Ne:CCl4 sample is codeposited at approximately 5 K with a beam of neon atoms that have been excited in a microwave discharge, the infrared spectrum of the resulting deposit includes prominent absorptions not only of CCl3 but also of several other neutral and ionic species. The absorptions assigned to CCl3+, CCl2+, and CCl+ are consistent with previous spectroscopic identifications of these species. As at lower energies, the Cl2CCl⋅⋅Cl isomer of CCl4 contributes to the product spectrum. Higher level ab initio calculations of the fundamental vibrations of this isomer and of its carbon-13 substituted counterpart give improved agreement with the experimentally observed infrared spectrum and, together with the results of a supplementary experiment, provide further support for the assignment of a structured absorption near 500 cm−1 to this species, rather than to Cl3+. Uncharged Cl2CCl⋅⋅Cl is readily destroyed by visible radiation, with concomitant growth in the absorptions of CCl4. Photodestruction of ionic species occurs in the ultraviolet spectral region. Evidence is presented for the stabilization of Cl2CCl⋅⋅Cl− and of Cl3CCl− in these experiments. The latter species undergoes photodestruction in the near infrared spectral region. Two absorptions are tentatively assigned to the ClCCl⋅⋅Cl− fragment ion.

Polarization-gradient cooling in a strong doughnut-mode dipole potential

We present experimental and theoretical studies of polarization-gradient cooling of metastable neon atoms confined to the dark center of a ${\mathrm{TEM}}_{01}^{*}$ (doughnut) mode. A slow beam of neon atoms is guided and focused inside a blue-detuned and focused doughnut-mode laser beam to a spot size below 10 \ensuremath{\mu}m. The transverse motion inside this doughnut mode is cooled by means of two-dimensional optical molasses. We observed non-Gaussian two-component velocity distributions of which the cold component has a width of down to three recoil velocities. These results are found to be in qualitative agreement with a quantum Monte Carlo simulation of cooling in one dimension in the presence of an external light-shift potential. For the simulation we apply the recently developed technique of quantum-state diffusion with adaptive noise.

Experimental and ab initio study of the infrared spectra of ionic species derived from PF5, PF3, and F3PO and trapped in solid neon

When a Ne:PF5 or a Ne:PF3 mixture is codeposited at 5 K with a beam of neon atoms that have been excited in a microwave discharge, the infrared spectrum of the resulting solid shows a complicated pattern of new absorptions. Little fragmentation of PF5 into PF3 occurs, but several of the absorptions can be tentatively attributed to PF4. The results of extensive ab initio calculations of the vibrational spectra of the neutral, cation, and anion species of formula PFn are presented, in order to aid in the product identification. Several absorptions of PF4+, PF3+, and PF2+ are identified, with only PF3+ common to both systems. Other prominent absorptions are contributed by PF5−, PF4−, and PF3−. In all of the Ne:PF5 experiments and some of the Ne:PF3 experiments, F3PO was a major contaminant. Therefore, ab initio calculations were also conducted for most of the neutral and charged species that can result from F3PO. There is strong evidence supporting the identification of two of the vibrational fundamentals of F3PO−, and some evidence for a third. Tentative assignments are suggested for neutral and other charged species derived from F3PO.

Energy transfer in rare gas collisions with self-assembled monolayers

A molecular dynamics simulation is presented of a beam of neon atoms scattering off a n-hexyl thiolate self-assembled monolayer adsorbed on a Au {111} surface. Ab initio QCISD(T)/6-311++G** calculations, for a model system consisting of a neon atom and a methane molecule, were used to derive an accurate interaction potential between the neon projectile and the monolayer. Four initial translational energies of 1.2, 5, 20, and 40 kcal/mol and five incident angles (with respect to the surface normal) of 10, 30, 45, 60, and 80 degrees were investigated in the simulations. Both trapping desorption and direct inelastic scattering collisional events were observed. The fraction of trapping desorption decreases as the initial translational energy and/or the angle of incidence increases. For high initial translational energy, trapping desorption may involve penetration of the monolayer. The overall energy transfer probability and the fraction of trapping desorption are in good agreement with previous experiments [J. Chem. Phys. 99, 7056 (1993)] and computational studies [J. Chem. Phys. 100, 8408, 6500 (1994)] of neon atom beams colliding with liquid squalane surfaces. There is a small but measurable change in the energy transfer efficiency for neon atoms colliding parallel versus perpendicular to the “tilt angle” of the SAM. The distributions of the change in the azimuthal angle and the scattering angle between the neon final velocity vector and surface normal provide additional information about the collision dynamics. A general discussion of these simulation results is given, in the context of existing models and theories for gas/surface collisions, to achieve a more fundamental understanding of the dynamics of interfaces.

Holographic manipulation of an atomic beam

The experimental result on the holographic manipulation of a laser-cooled metastable neon atomic beam with a SiN thin-film binary hologram is described. Several new techniques of holographic manipulation are proposed and discussed.

Observation of Two-Atom Correlation of an Ultracold Neon Atomic Beam.

The intensity correlation spectrum of an ultracold ${}^{20}\mathrm{Ne}$ atomic beam in the ${1s}_{3}[{3s:}^{1}{P}_{0}]$ state is experimentally studied. The spectrum shows a peak around the origin with the width corresponding to the kinetic energy spread of atoms in the beam source.

Matrix isolation study of the interaction of excited neon atoms with BCl3: Infrared spectra of BCl+3, BCl+2, and BCl−3

When a Ne:BCl3 sample is codeposited at approximately 5 K with a beam of neon atoms that have been excited in a microwave discharge, the infrared spectrum of the resulting solid deposit shows a weak to moderately intense absorption of BCl2 and more prominent absorptions which are assigned to the ν3 fundamentals of BCl+3 (D3h) and of linear, centrosymmetric BCl+2. The boron- and chlorine-isotopic structure of the spectrum is consistent with both of these assignments. Ab initio calculations support the BCl+2 assignment. An absorption is also tentatively assigned to ν3(e) of BCl−3. Ab initio calculations for BCl−3 are consistent with that assignment. The processes which occur when the solid deposit is exposed to visible and ultraviolet radiation are considered.

The vibrational spectra of molecular ions isolated in solid neon. XII. HCl+, (HCl)+2, ClHCl−, and O2⋅⋅HCl+

When a Ne:HCl or a Ne:DCl sample is codeposited at approximately 5 K with a beam of neon atoms that have been excited in a microwave discharge, the infrared spectrum of the solid deposit includes the fundamental absorption of HCl+ or DCl+, which appears about 1% below the corresponding gas-phase band center. Another absorption, intermediate between the fundamentals of HCl and of HCl+, is contributed by an HCl-stretching fundamental of (HCl)+2. Among the important anion species present in the solid is ClHCl−, infrared absorptions of which are identified. Charge delocalization is sufficiently reduced in solid neon, compared to the heavier rare gases, that ion production from HCl does not occur at or below 10.2 eV. The electric field of the ions trapped in solid neon inhibits the rotation of HCl and leads to the appearance of a prominent HCl Q-branch absorption. In the presence of traces of oxygen, the O2⋅⋅HCl+ complex is stabilized, as evidenced by the appearance of the OO- and HCl-stretching absorptions of that species. The two O atoms are equivalent or nearly equivalent in the complex. It is suggested that photoexcitation of O2⋅⋅HCl+ leads to charge exchange, producing O+2 and HCl, with a threshold near 370 nm.