Excited State Lines Research Articles

Cesium excited state line shapes from 6P-9S and 5D-10F broadened by helium, argon, and methane

Pump modulated laser absorption spectroscopy was used to measure the cesium 62P1/2→92S1/2 and 52D5/2→102F5/2,7/2 line shapes with helium, argon, and methane used as collision partners. The broadening rates are 99.5±3.4, 116.6±1.8, 188.2±3.3, 133.2±1.2, 294±4.5, and 710±18 MHz/Torr for He, Ar, and CH4 in 6P−9S and 5D−10F respectively, while the shift rates are +121±21, - 29.3±21, - 61±16, +101.4±0.8, - 273.0±8.0, and - 231±29 MHz/Torr. For those same transitions, the asymmetry rates are +0.18±0.15, - 3.1±0.14, - 3.2±0.1, +0.14±0.04, and - 0.32±0.22 mrad/Torr, with no reported value for CH4 along 5D−10F. Broadening rates scale as expected with polarizability, shift direction is to the blue/red with He/other gases, and the direction of the asymmetry correlates to the shift.

Coherent Optical Creation of a Single Molecule

We report coherent association of atoms into a single weakly bound NaCs molecule in an optical tweezer through an optical Raman transition. The Raman technique uses a deeply bound electronic excited intermediate state to achieve a large transition dipole moment while reducing photon scattering. Starting from two atoms in their relative motional ground state, we achieve an optical transfer efficiency of 69%. The molecules have a binding energy of 770.2MHz at 8.83(2)G. This technique does not rely on Feshbach resonances or narrow excited-state lines and may allow a wide range of molecular species to be assembled atom-by-atom.

Rubidium excited state line shapes from [formula omitted] to [formula omitted] and [formula omitted] broadened by helium

Pump modulated laser absorption spectroscopy was used to measure five excited state line shapes for electric dipole allowed transitions beginning in the Rb 5P manifold. Helium was used as the collisional buffer gas, with pressures from 0 to 250 Torr. Center frequency, FWHM, and asymmetry parameters were extracted from the fits and plotted versus pressure to determine rates. Lines terminating in the 5D manifold had collisional broadening rates, γ, of 49.5–54.6 MHz/Torr, collisional shift rates, δ of less than ±1.3 MHz/Torr, and asymmetry rates, β0, of less than ±0.08 mrad/Torr. Lines terminating in the 72S1/2 state showed significantly higher rates, with broadening rates of 109.1–111.0 MHz/Torr, shift rates of 11.5–13.3 MHz/Torr, and asymmetry rates of 0.28–0.47 mrad/Torr. These trends qualitatively match numerically computed difference potentials, which also predict large rates for the 7S lines and smaller rates for the 5D lines.

HD 150382: A Lithium-rich Star at the Early-AGB Stage?*

Abstract We report the discovery of a lithium-rich giant, HD 150382, a post-red-giant-branch clump star. The atmospheric parameters, the chemical abundances for 17 elements, and the isotopic ratio 12C/13C were determined using the equivalent width and the spectral synthesis methods. The lithium abundance was determined via spectral synthesis of the Li i resonance doublet at λ 6708 yielding log ϵ(Li)NLTE = 2.55. The excited-state line at λ 6104 also was analyzed. In addition, we have used theoretical evolutionary tracks to determine the mass and luminosity of HD 150382 and compare it with other well-known lithium-rich giants in the literature. Our results show that HD 150382 is a slowly rotating K-giant star having near-solar metallicity. We also show that HD 150382 is not s-process enriched, which is in agreement with its evolutionary status. Finally, based on the abundance results, we study the possible scenarios of the lithium enrichment.

Determination of a semi-experimental equilibrium structure of 1-phosphapropyne from millimeter-wave spectroscopy of [formula omitted] and [formula omitted

Trideuterated 1-phosphapropyne (CD3CP) has been produced by co-pyrolysis of phosphorus trichloride and esadeuterated ethane. The rotational spectra of CD3CP in the ground and the low-lying vibrational states v8 (CCP bending mode) and 2 v8 have been investigated in the millimeter-wave region. Very accurate values of the quartic centrifugal distortion constants DJ and DJK and of the sextic distortion constants HJK and HKJ have been obtained for the ground state. l-type resonance effects have been taken into account in the analysis of the spectra of the degenerate bending states, so that the energy difference between the v8|l| = 20, and v8|l| = 22 states could be determined, together with a number of spectroscopic constants involved in the l-type resonance. Moreover, for the parent isotopologue CH3CP a new set of excited-state lines (v8 = 1, 2 and v4 = 1) were recorded up to 330 GHz, and a global analysis including all available rotational and rovibrational transitions related to the ground and v8 = 1, 2 states has been performed. A satisfactory fit could only be obtained by making a reassignment of the few transition wavenumbers previously measured for the 2ν80←ν8±1 hot band [M.K. Bane et al., J. Mol. Spectrosc.275 (2012) 9–14].The experimental work has been combined with quantum-chemical computations. Quadratic and cubic force constants of 1-phosphapropyne have been calculated at MP2 level of theory with a basis set of triple-ζ quality. A semi-experimental equilibrium structure has been derived by correcting experimental ground-state rotational constants by means of theoretical vibration-rotation interaction constants.

Correlating Photoluminescence and Structural Properties of Uncapped and GaAs-Capped Epitaxial InGaAs Quantum Dots

The understanding of the correlation between structural and photoluminescence (PL) properties of self-assembled semiconductor quantum dots (QDs), particularly InGaAs QDs grown on (001) GaAs substrates, is crucial for both fundamental research and optoelectronic device applications. So far structural and PL properties have been probed from two different epitaxial layers, namely top-capped and buried layers respectively. Here, we report for the first time both structural and PL measurements from an uncapped layer of InGaAs QDs to correlate directly composition, strain and shape of QDs with the optical properties. Synchrotron X-ray scattering measurements show migration of In atom from the apex of QDs giving systematic reduction of height and enlargement of QDs base in the capping process. The optical transitions show systematic reduction in the energy of ground state and the first excited state transition lines with increase in capping but the energy of the second excited state line remain unchanged. We also found that the excitons are confined at the base region of these elliptically shaped QDs showing an interesting volume-dependent confinement energy scaling of 0.3 instead of 0.67 expected for spherical dots. The presented method will help us tuning the growth of QDs to achieve desired optical properties.

ON THE ORIGIN OF WIND LINE VARIABILITY IN O STARS

We analyze 10 UV time series for 5 stars which fulfill specific sampling and spectral criteria to constrain the origin of large-scale wind structure in O stars. We argue that excited state lines must arise close to the stellar surface and are an excellent diagnostic complement to resonance lines which, due to radiative transfer effects, rarely show variability at low velocity. Consequently, we splice dynamic spectra of the excited state line, N IV1718, at low velocity to those of 1393 component of the Si IV 1400 doublet at high velocity in order to examine the temporal evolution of wind line features. These spliced time series reveal that nearly all of the features observed in the time series originate at or very near the stellar surface. Further, we positively identify the observational signature of equatorial co-rotating interaction regions in two of the five stars and possibly two others. In addition, we see no evidence for features originating further out in the wind. We use our results to consolidate the fact that the features seen in dynamic spectra must be huge, in order to remain in the line of sight for days, persisting to very large velocity and that the photospheric footprint of the features must also be quite large, ~ 15 - 20% of the stellar diameter.

Water in star-forming regions withHerschel(WISH)

To understand the origin of water line emission and absorption during high-mass star formation, we decompose high-resolution Herschel-HIFI line spectra toward 19 high-mass star-forming regions into three distinct physical components. Protostellar envelopes are usually seen as narrow absorptions or emissions in the H2O 1113 and 1669 GHz ground-state lines, the H2O 987 GHz excited-state line, and the H2O-18 1102 GHz ground-state line. Broader features due to outflows are usually seen in absorption in the H2O 1113 and 1669 GHz lines, in 987 GHz emission, and not seen in H2O-18, indicating a low column density and a high excitation temperature. The H2O 1113 and 1669 GHz spectra show narrow absorptions by foreground clouds along the line of sight, which have a low column density and a low excitation temperature, although their H2O ortho/para ratios are close to 3. The intensities of the H2O 1113 and 1669 GHz lines do not show significant trends with luminosity, mass, or age. In contrast, the 987 GHz line flux increases with luminosity and the H2O-18 line flux decreases with mass. Furthermore, appearance of the envelope in absorption in the 987 GHz and H2O-18 lines seems to be a sign of an early evolutionary stage. We conclude that the ground state transitions of H2O trace the outer parts of the envelopes, so that the effects of star formation are mostly noticeable in the outflow wings. These lines are heavily affected by absorption, so that line ratios of H2O involving the ground states must be treated with caution. The average H2O abundance in high-mass protostellar envelopes does not change much with time. The 987 GHz line appears to be a good tracer of the mean weighted dust temperature of the source, which may explain why it is readily seen in distant galaxies.

BAL OUTFLOW CONTRIBUTION TO AGN FEEDBACK: FREQUENCY OF S IV OUTFLOWS IN THE SDSS

We present a study of Broad Absorption Line (BAL) quasar outflows that show S IV ?1063 and S IV* ?1073 troughs. The fractional abundance of S IV and C IV peak at similar value of the ionization parameter, implying that they arise from the same physical component of the outflow. Detection of the S IV* troughs will allow us to determine the distance to this gas with higher resolution and higher signal-to-noise spectra, therefore providing the distance and energetics of the ubiquitous C IV BAL outflows. In our bright sample of 156 SDSS quasars 14% show C IV and 1.9% S IV troughs, which is consistent with a fainter magnitude sample with twice as many objects. One object in the fainter sample shows evidence of a broad S IV trough without any significant trough present from the excited state line, which implies that this outflow could be at a distance of several kpc. Given the fractions of C IV and S IV, we establish firm limits on the global covering factor on S IV that ranges from 2.8% to 21% (allowing for the k-correction). Comparison of the expected optical depth for these ions with their detected percentage suggests that these species arise from common outflows with a covering factor closer to the latter.

Non-delta-function electronic spectral densities in individual quantum dots

Using a simplified model approach we estimate the optical line shape of the transition lines observable in photoluminescence experiments on quantum dots. We use the theory based on the interaction of electrons with the longitudinal optical phonons only. This theory gives, in the self-consistent Born approximation, the lowest-energy excited state line shape in the form of a very narrow peak with a shoulder on the low-energy side. We turn the attention to a comparison with experiments which appear to support this theoretical conclusion. This agreement emphasizes the role of the electronic multiple scattering on optical phonons in quantum dots. It is demonstrated that the optical line shape can give an information about the quantum dot system.

Analysis of Rotational Transitions of Methyl Formate in the Ground and First Excited Torsional States

The microwave spectrum of methyl formate has been observed in the 7−200 GHz region, and new 437 lines have been assigned to the first excited A torsional substate. Both excited state lines and ground state lines reported previously were analyzed simultaneously on the basis of an internal axis method Hamiltonian. A total of 3514 lines were fitted to a 10th-order reduced Hamiltonian model involving 67 molecular parameters to a 1σ standard deviation of 179 kHz.

Space Telescope Imaging Spectrograph Observations of High‐Velocity Interstellar Absorption‐Line Profiles in the Carina Nebula

An atlas of ultraviolet interstellar absorption-line profiles toward four stars in the Carina Nebula is presented. The observations have been made with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope, with a resolving power of 114,000. Low-ionization, high-ionization, and excited-state lines from a wide array of chemical species are included. Extensive measurements of radial velocities, velocity dispersions, and column densities of individual components in these profiles are also given. The unprecedented capabilities of STIS reveal many more velocity components than previously known; most of the high-velocity components in previous observations with the International Ultraviolet Explorer are now resolved into multiple subcomponents, and even higher velocities are seen. The great range of line strengths available permits the detection of the low-velocity components in the weakest lines, and progressively higher velocities in stronger lines (in which the low-velocity components become completely blended). The weak and high-ionization lines trace global structure in the H II region, while the strong low-ionization lines show intricate high-velocity structure that likely originates relatively near to the O stars observed. The extreme velocities found in the low-ionization lines toward these four stars are -388 and +127 km s-1, with 23-26 resolved components in each. Some components in different stars may be related, but many are different in each line of sight. A remarkably well-defined Routly-Spitzer effect is found in this region. Temporal variations toward one star observed twice have already been reported. These measurements will be used in subsequent astrophysical analyses to further constrain the origins of the phenomena.

Metastable chalcogen-related luminescent centers in silicon.

Selenium-doped silicon quenched after heat treatment at 800 \ifmmode^\circ\else\textdegree\fi{}C exhibits deep luminescence similar to that previously reported in sulfur-doped silicon. The corresponding Se-related complex gives rise to two deep bound-exciton (BE) photoluminescence (PL) emissions, which at low temperature have no-phonon (NP) lines at 955.5 meV (${\mathrm{Se}}_{\mathit{A}}^{0}$) and 772.2 meV (${\mathrm{Se}}_{\mathit{B}}^{0}$), respectively. A series of equidistant phonon replicas is observed with the same phonon energy as in the sulfur case. By increasing the temperature in the PL experiments associated BE excited-state lines are detected higher in energy with a separation of 10.5 and 12.4 meV, respectively, from the lowest NP lines. The metastability of both the S- and Se-related defects is investigated and discussed as well as the influence of the excitation photon energy on the intensity of the PL emission. The metastability is also confirmed by optically detected magnetic-resonance results, which also show that the (${\mathrm{S}}_{\mathit{A}}^{0}$) and (${\mathrm{Se}}_{\mathit{A}}^{0}$) lines correspond to an excited spin-triplet state. Both defects are found to have a low symmetry. When they are in the A configuration the symmetry is monoclinic I with one axis tilted approximately 20\ifmmode^\circ\else\textdegree\fi{} from the [11\ifmmode\bar\else\textasciimacron\fi{}1] axis in the (110) plane.

Millimeter-wave spectrum of NCS radical in the ground 2Π state

The rotational transitions of NCS have been observed in the 1 to 3 mm wavelength region in a hollow cathode discharge in a gas mixture of CS2 (∼1 mTorr) and N2 (∼30 mTorr). The molecular constants in the ground state are determined by fitting the observed frequencies to the standard Hamiltonian for 2Π states. The accuracy of the molecular constants are greatly improved compared with the values obtained from the optical data. The lines in the excited vibronic states have also been observed. The analysis including those excited state lines is in progress and the results will be published separately.

The laboratory millimeter- and submillimeter-wave spectrum of the first two excited torsional states of (C-13)H3OH

The rotational-torsional spectrum of (C-13)H3OH is presented in both the symmetric and degenerate substates of the first two excited torsional states. Of the new transitions reported, 122 lines are from the v(t) = 1 torsional state and 110 lines are from the v(t) = 2 torsional state, and all are confined to the rotational quantum number J = 8 or less. The data are combined with previously reported millimeter and submillimeter data for the v(t) = 0 torsional state and 44 previously measured excited torsional state lines to form a global data set of 596 transitions, which is analyzed and fitted using an extended internal axis method. The fit results in an overall rms deviation of 1.98 MHz. The spectral constants generated by the fit are used to predict an additional 123 lines of (C-13)H3OH in the v(t) = 1,2 excited torsional states with frequencies up to 612 GHz and rotational quantum number J = 11 or less.

Measurement of relative oscillator strengths for Mn I. Transitions from levels in the range 0 eV < < 3 eV

We present relative oscillator strengths for 58 lines of Mn I for a range of + 0.19 > log(gf) > −3.795 in the excitation interval 0eV < χ < ∼ 3 eV. The measurements have been made to a relative accuracy of better than 2 per cent using the Oxford furnace tehnique, with full allowance for hyperfine structure using the data of Booth et al. The relative values have been placed on an absolute scale using published lifetime data, to an accuracy of about 7 per cent for the ground state lines and 3 per cent for the excited state lines.

Additional structure in infrared excitation spectra of group-III acceptors in silicon

High-resolution infrared ${p}_{\frac{3}{2}}$ and ${p}_{\frac{1}{2}}$ excitation spectra are reported for the group-III acceptors boron, aluminum, gallium, and indium in silicon. New lines, which are believed to be due to previously unresolved excited states, are observed in the ${p}_{\frac{3}{2}}$ spectra. A $5{p}^{\ensuremath{'}}$ line is observed for the first time in the gallium spectrum. Some previously reported boron ${p}_{\frac{3}{2}}$ lines are relabeled to correspond with the other group-III spectra. A feature in each of the ${p}_{\frac{3}{2}}$ spectra is defined as ${E}_{I}$, the ground-state binding energy. Values measured for ${E}_{I}$ are 44.39, 69.03, 72.73, and 155.58 (\ifmmode\pm\else\textpm\fi{}0.02) meV for B, Al, Ga, and In, respectively. The data show more complete correspondence between all the group-III excited-state lines than any previously published. The spin-orbit splitting of the valence bands is experimentally deduced to be 44.00\ifmmode\pm\else\textpm\fi{}0.02 meV.

Additionalp32andp12infrared excited-state lines of gallium and indium in silicon

Infrared excitation spectra were measured for the ${p}_{\frac{3}{2}}$ lines of gallium in silicon. Two missing lines were observed, and a previous weak or doubtful one was confirmed. Spectra were also obtained of the ${p}_{\frac{1}{2}}$ lines of gallium and indium in silicon, demonstrating for the first time the $4{p}^{\ensuremath{'}}$ line for both dopants. There now exists complete correspondence between all observed excited-state lines of gallium and indium in silicon and the lines of boron and aluminum, and with those predicted by theory. From the new spectral data, the spin-orbit splitting of the valence bands is calculated to be 42.62\ifmmode\pm\else\textpm\fi{}0.04 meV.

Observation of additional excited-state lines of indium in silicon

Absorption spectra in the region 1100 to 1300 ${\mathrm{cm}}^{\ensuremath{-}1}$ for silicon which has an indium concentration of approximately 4.2 \ifmmode\times\else\texttimes\fi{} ${10}^{16}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ are presented. The spectra were obtained with both grating and Fourier-transform spectrophotometers. Previously unreported indium excited-state lines are observed, and the existence of a line previously reported as weak or doubtful is confirmed. The energy-level spacings for the additional indium lines are shown to be in good agreement with the energy-level spacings for the corresponding boron, aluminum, and gallium lines.

Infrared-microwave double resonance in CF 3I; Microwave spectroscopy in emission and absorption

From the double resonance effects observed on the microwave spectrum of CF 3I it has been shown that the R(16) CO 2 laser line of the 9.4 μm band is coincident with the R(7), K = 2, F = 19 2 → 21 2 transition of the CF 3, symmetric stretch ( ν 1 band) of CF 3I. Using this laser line, 50 double resonance signals all with K = 2 were observed ranging from J = 4 → 5 to J = 12 → 13 transition. The fact that double resonance effects were observable over such a large range of J was explained as being caused by very strong Δ J = ± 1, Δ K = 0 collisional transitions. Extremely large pumping effects were produced using 6 W of laser radiation, which caused relative changes in intensity ( ΔI I ) in ground state lines of up to 25. The population transfer into the excited state was so large that many excited state lines, which had previously been undetectable, produced signals up to 30 times more intense than the corresponding undisturbed ground state lines (i.e., values of ΔI I of ∼6000 were achieved). Population inversions were produced by the laser pump in many of the K = 2 microwave transitions, not only in those with levels directly pumped by the laser but also in some connected only by collisional transitions. The results was that many of the signals were observed as stimulated emissions rather than absorptions. The rotational constant and quadrupole coupling constants of CF 3I in the v 1 excited state are calculated and an estimation of the center of the ν 1 band is made. The absolute population shifts produced by the laser pump are estimated and the rate constants of the collisional transitions are discussed.