Metastable 2D Research Articles

Measurement of the 2D5/2–2D3/2 fine structure interval in metastable nitrogen atoms at 1.15 mm by laser magnetic resonance

Far infrared laser magnetic resonance (LMR) spectra of metastable (2p3)2D nitrogen atoms have been measured using laser lines in carbonyl fluoride (COF2) at 1135 μm and methanol (CH3OH) at 1224 μm. The concentration of N 2D was optimized by electron paramagnetic resonance (EPR) using a hybrid EPR/LMR spectrometer. The far infrared cavity of this spectrometer was designed to oscillate at wavelengths longer than 1 mm. The LMR spectra were analyzed using g factors derived from the EPR spectrum [Radford and Evenson, Phys. Rev. 168, 70 (1968)] and yield a precise value of the 2D5/2–2D3/2 fine structure separation of −261 447.7(2) MHz, −8.720 957(7) cm−1(2σ).

The location of the CA II ions in the beta Pictoris disk

view Abstract Citations (55) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Location of the CA II Ions in the Beta Pictoris Disk Hobbs, L. M. ; Lagrange-Henri, A. M. ; Ferlet, R. ; Vidal-Madjar, A. ; Welty, D. E. Abstract Echelle spectra of beta Pictoris have been obtained in the region of the Ca II 8542A line which arises from the metastable 3d 2D5/2 level. A narrow, weak, circumstellar absorption line is seen at the stellar radial velocity. A simple theory is developed of the radiative pumping of the metastable levels of the Ca II ions by the radiation from the star at the H and K lines. The relatively large fractional population, N3(Ca II)/N1(Ca II) of roughly 0.05, observed for the metastable level then requires that the calcium absorbers be largely concentrated within about 1 AU of the star. This result confirms two previous, independent estimates of the location of this gas. A time-variable circumstellar component of the 8542A line also is found at an infall velocity of about 15 km/s. Publication: The Astrophysical Journal Pub Date: November 1988 DOI: 10.1086/185308 Bibcode: 1988ApJ...334L..41H Keywords: Atomic Energy Levels; Calcium; Line Spectra; Stellar Envelopes; Absorption Spectra; Echelle Gratings; Interstellar Extinction; Parity; Radial Velocity; Astrophysics; LINE FORMATION; STARS: CIRCUMSTELLAR SHELLS full text sources ADS | data products SIMBAD (2)

On the Long-Lived Excited State of Ar II

Time-of-flight energy spectra of Ar atoms produced through charge transfer reactions in collisions of Ar + (metastable Ar M+ ) ions with Ne atoms have been measured at a collison energy of 50 eV. Two prominent peaks appear at exoergicities of about 0.35 and 1 .5 eV. The measurement of the appearance energies of these peaks suggests that the 0.35 eV peak is due to metastable 3d' 2 F 7/2 ions and that the 1.5 eV peak is an indication of the existence of an unknown long-lived excited Ar + state.

ChemInform Abstract: The Effect of Incident Spin‐Orbit State on the Chemiluminescent Reactions of Ba(3DJ) with Several Oxidants

Abstract(Cl2, Br2, CCl4, N2O, and NO2) is determined by utilizing optical pumping state selection.

Spin–orbit effects in chemical reactions. Investigation of ground-state products from reactions of Ba(3D)

The dependence of the cross-sections for production of ground-state barium halide products on incident spin–orbit state has been determined by means of optical-pumping state selection for the reaction of metastable Ba(6s5d3D) with HCl, CH3Cl, HBr and CH3Br. In addition, cross-sections for the metastable 1D level were related to those of the 3DJ multiplet by optical pumping on an intercombination line. For alkyl halide (RX) reactants, the spin–orbit dependence of the reactivity for the ground-state channel was substantial with an ordering J= 1 > J= 2 > J= 3. This is an opposite ordering to that previously observed for the chemiluminescence channels in analogous reactions. The hydrogen halide reactions exhibited a varying spin–orbit dependence with vibrational level. For the most highly populated vibrational levels v, the spin–orbit dependence was comparable in sign and magnitude to that for RX reactants, while a significantly diminished variation of reactivity with incident J was observed for lower v. The variation of spin–orbit effect with product vibrational level is believed to be due to the dependence of the reaction dynamics on incident impact parameter.

‘Quantum jumps’ observed in the fluorescence of a single ion

The laser-excited resonance fluorescence of a single Ba + ion at 493 nm shows interruptions of macroscopic time durations when the ion drops into a dark state by off-resonant Raman scattering, or by weak excitation of the 2P 3/2 level. We manipulate the ion out of the state by auxiliary laser light and prove that state to be the metastable 2D 5/2 level. Fluorescence from three ions displays an enhanced rate of multiple “jumps” which reveals cooperative ionic interaction with the light.

The effect of incident spin-orbit state on the chemiluminescent reactions of Ba(3D J) with several oxidants

The dependence of the chemiluminescence channels on incident spin-orbit state has been determined by utilizing optical pumping state selection for the reactions of metastable Ba(6s5d 3DJ) with Cl2, Br2, CCl4, N2O, and NO2. The cross sections for the neighboring metastable 1D level were related to those for the 3DJ multiplet by optical pumping on an intercombination line. For the halogen-containing reagents, the spin-orbit dependence of the reactivity was substantial for BaX B–X emission and was in the order J=3>J=2>J=1. The differences in reactivity were somewhat less for the C–X chemiluminescence channel in the Cl2 and Br2 reactions. Essentially no spin-orbit dependence was observed in the N2O and NO2 reactions.

Hyperfine structure measurements of the metastable (3d 6 4s 2)3 H 4, 5, 6 states of57Fe: Configuration interaction in the hyperfine structure of the iron atom

We report the hyperfine structure (hfs) measurement of the metastable (3d6 4s2)a3H4, 5, 6 states of57Fe. The kHz-precision of these experimental results together with the hyperfine structure values of (3d6 4s2)a5D1, 2, 3, 4, (3d7 4s)a5F2, 3, 4, 5, and (3d7 4s)a3F2, 3, 4, which were measured earlier, allowed to determine a very detailed set of effective radial parameters describing the hfs of these states, using a new parametrization method. This method treats one- and two-body contributions to the hfs separately. In this way configuration interaction effects in the hfs of the57Fe atom can be studied in detail and compared with configuration interaction effects in the fine structure of the same atom.

Single‐collision chemiluminescence study of the Ba(1S,3D)+NO2, N2O, O3reactions

Chemiluminescence from the reactions of Ba ground state 6s2 1S and metastable 6s5d 3D atoms with NO2, N2O, and O3 has been studied under single-collision conditions. Spectra, chemiluminescence cross sections, and photon yields for production of BaO* are reported. In the Ba(3D)+N2O and Ba(1S, 3D)+O3 reactions, a red feature, not previously reported, has been observed and tentatively assigned as BaO D 1Σ+–A 1Σ+ emission. The dynamics of these reactions and the differences between the Ba and lighter alkaline earth atom reactions are discussed.

Excitation by electron capture in collisions of ground state and metastable Ne2+with Xe at 40 keV

The optical attenuation method (OAM) developed recently by Matsumoto et al. (1980) has been extended to photon emission in the VUV spectral region to investigate initial- to final-state selective electron capture in Ne2+-Xe collisions at 40 keV. One-electron-capture cross sections for Ne2+ ions in their 3P ground state were found to be only one half of that for the metastable 1D ions which is explained by a larger contribution from transfer ionisation for the latter. With these results initial- to final-state selective excitation cross sections for the most important electron capture channels were derived and found to be consistent with the corresponding total one-electron-capture cross section.

Laser-rf double-resonance hyperfine structure measurements of the metastable 3d 4s 1 D 2 state of43Ca

The hyperfine structure of the (3(d 4s)1 D 2metastable state of43Ca has been measured using theABMR-LIRF method (atomic beam magnetic resonance, detected by laser induced resonance fluorescence). The measurements yielded for the magnetic dipole and electric quadrupole constantsA=−17.650(2) MHz andB=−4.642(12) MHz, respectively. From the measuredB factor the spectroscopic electric quadrupole moment (uncorrected for shielding effects) has been calculated to beQ(43Ca)=−0.062(12) barn. In addition, isotope shifts in the lines (3d 4s)1 D 2(3d 4p)1 F 3 0 and (3d 4s)1 D 2(4s 5p)1 p 1 0 for the stable calcium isotopes have been obtained by high resolution laser spectroscopy.

The SrCl(AX, BX) bands in thermal and non-thermal reactive excitation using metastable Sr atoms

The emission of SrCl spectra in the AX, BX bands is studied in chemical reactions of Sr atoms in the metastable 1D and 3P states with HCl, CCl 4, Cl 2, ICl under bimolecular collision conditions. The spectral shape is strongly non-thermal and has peaks at the positions of sequence turnings. In order to interpret the structure also SrCl spectra in thermal equilibrium were excited using the newly developed gas-dynamic jet source. The source with additional discharge along the jet is described, and its utility as a new light source for molecular spectroscopy is outlined. Numerous discrepancies in the current literature concerning the spectroscopy of SrCl are revealed and are mostly removed. Taking into account the influence of vibration onto the formation of rotational heads the structure of the reactive spectra is interpreted. Differences with respect to the spectra in analogous Ca reactions are described. Improvements for the study of reactions of excited atoms are proposed.ft]*|Present address: Universität/Gesamthochschule Wuppertal, Fachbereich Chemische Physik, D-5600 Wuppertal, FRG.

Characterization of a nitrogen atom beam by magnetic selection analysis

A nitrogen atom beam produced by a He-N 2 microwave discharge has been characterized using magnetic selection and mass spectrometry. The relative composition N/N 2 in the beam is ≈ 9%. The nitrogen atoms are nearly all in the two metastable states 2D J and 2P J , with relative population ≈ 2.5 : 1.

The Rate Constants of the Reactions of the Metastable Nitrogen Atoms, 2D and 2P, and the Reactions of N(4S)+NO→N2+O(3P) and O(3P)+NO+M→NO2+M

Abstract The pulse-radiolysis technique was used for the measurement of the quenching rates of the metastable nitrogen atoms, 2D and 2P, both in nitrogen and in helium. The rate constants obtained for N(2D) were (1.3±0.2)×10−14 cm3 molecule−1 s−1 (1 cm3 molecule−1 s−1=6.022×1017 m3 mol−1 s−1) in nitrogen and (4.6±0.4)×10−17 in helium; these values were larger than those for the higher energy metastable nitrogen atoms, N(2P), (3.3±0.3)×10−17 in nitrogen and (4.2±1.3)×10−18 in helium. The room temperature rate constants of the reactions of these atoms with nitrogen monoxide and with ethylene were also measured. All of these rate constants were found to be of the order of 3×10−11 cm3 molecule−1 s−1. The rate constants of the reactions, N(4S)+NO→N2+O(3P) and O(3P)+NO+M→NO2+M, were also measured and compared with literature values.

O-scattering by noble gases

O- scattering by Ne, Ar and Kr in the 0.2-1 keV laboratory energy range has been studied. The energy-loss spectra of scattered particles were obtained using the time-of-flight method and electrostatic analysis. Reduced differential cross-sections for elastic and inelastic processes are reported in the 0-5 keV deg. angular range. The dominant inelastic process is found to be single electron detachment leading to the formation of oxygen in the ground 3P and metastable 1D states. A method of forming a metastable 1D oxygen beam is proposed. O+ production was observed for O--Ne collisions, however this process does not appear to be important in the energy and angular range studied. The results are discussed within a quasimolecular framework.

Charge exchange of metastable 2D oxygen ions with N 2 in the thermosphere

Measurements of N 2 + and supporting data made on the Atmosphere Explorer-C satellite in the ionosphere are used to study the charge exchange process O +( 2 D)+ N 2 → k N + 2+ O The equality k = (5 ± 1.7) × 10 −10cm 3 s −1. This value lies close to the lower limit of experimental uncertainty of the rate coefficient determined in the laboratory. We have also investigated atomic oxygen quenching of O +( 2D) and find that the rate coefficient is 2 × 10 −11 cm 3s −1 to within approximately a factor of two.

On the chemistry of metastable atomic nitrogen in theFregion deduced from Simultaneous satellite measurements of the 5200-Å airglow and atmospheric composition

The 5200-A N I (4S-²D) emission monitored by the visible airglow experiments on Atmosphere Explorer C and D combined with simultaneous measurements of atmospheric composition yields the following results. The metastable ²D term of atomic nitrogen must be produced in the F region at near the maximum rate allowed by currently accepted chemistry. The rate coefficient deduced for the loss of N(²D) by reaction with O2 is in good agreement with the laboratory result. The quenching rate of N(²D) by electrons lies in the range 3.6–6.5 × 10−10 (Te/300)1/2 cm³ s−1 if the laboratory rate for N2+ recombination is applicable to the thermosphere. The value may be somewhat larger than this if nonthermal effects are important. The quenching rate by atomic oxygen is near 4 × 10−13 cm³ s−1, much smaller than the laboratory value.

Kinetic energies and angular distributions of oxygen atom photofragments produced by photodissociation of O2 and N2O in the vacuum ultraviolet

A gas phase chemi-ionization process is used to detect O atoms produced by photodissociation of O2 and N2O. For the photon energies used here the accessible O atom states are within the ground 3P levels and the metastable 1D and 1S levels. Kinetic energies of the O atom photofragments are determined using an atomic beam time-of-flight technique, and the O atom angular distributions are determined by varying the angle between the direction of the photon beam and the atomic beam flight path. Dissociative transitions within the Schumman–Runge continuum of O2 and the principal vacuum ultraviolet absorption continuum of N2O yield results in agreement with previous predictions. For the dissociation of O2 at wavelengths of 120 and 124 nm, the principal dissociation products are O(3P)+O(1D); and, at these wavelengths, the O atom angular distribution is consistent with previous conclusions that predissociation is important. Using existing theories of photofragment angular distributions, an asymmetry parameter having a value of (−0.61±0.05) is obtained for predissociation in O2 at the 10.0 and 10.3 eV absorption features.

Carbon production in comet West 1975n

Rocket-ultraviolet spectra of comet West 1975n are reported which were obtained with scanning spectrophotometers in the wavelength range from 1200 to 1300 A. The principal emission features observed include lines of C, O, and C(+), as well as bands of OH, CO, CO(+). The estimated fluxes of the C, O, H, CO, and OH features are found to be consistent with a photodissociation source in which the CO evaporation rate is about one-third that of water. The presence of a large number of carbon atoms in the metastable 1D state is indicated and taken to suggest that dissociative recombination is important near the cometary nucleus, that CO must originate in the nucleus, and that CO is the primary carbon constituent of the comet.

Zero-field hyperfine structure measurements of the metastable states 3d 2 4s 4 F 3/2, 9/2 of45Sc using laser-fluorescence atomic-beam-magnetic-resonance technique

In an atomic beam experiment we measured the hyperfine structure (hfs) of the metastable states 3d 2 4s 4 F 3/2,9/2 of Scandium, which were populated by electron impact. A single mode cw dye laser was used to create a population difference between neighbouring hfs states by optical pumping. Rf transitions between these states, equalizing the population numbers, could then be detected by repeating the optical pumping experiment and looking for the laser induced fluorescent light. The following constants of the magnetic dipole and electric quadrupole interactions have been obtained by this method:A 3/2=−158.513(3)MHzB 3/2=−5.19(2)MHzA 9/2=285.967(9)MHzB 9/2=−15.46(70)MHz From these constants and the corresponding values forJ=5/2, 7/2, as measured by [1], the following parameters can be calculated: 〈r −3〉 01 =0.911(4)a 0 −3 〈r −3〉 12 =2.395 (62)a 0 −3 and:α=〈r −3〉 01 /〈r −3〉 12 =0.38(1).