arXiv subjects

E. J. Salumbides

Publications and source records attributed to E. J. Salumbides.

36 records · Page 2Linked to original sources

arXiv2016

Precision measurements and test of molecular theory in highly-excited vibrational states of H$_2$ $(v=11)$

Accurate $EF{}^1Σ^+_g-X{}^1Σ^+_g$ transition energies in molecular hydrogen were determined for transitions originating from levels with highly-excited vibrational quantum number, $v=11$, in the ground electronic state. Doppler-free two-photon spectroscopy was applied on vibrationally excited H$_2^*$, produced via the photodissociation of H$_2$S, yielding transition frequencies with accuracies of $45$ MHz or $0.0015$ cm$^{-1}$. An important improvement is the enhanced detection efficiency by resonant excitation to autoionizing $7pπ$ electronic Rydberg states, resulting in narrow transitions due to reduced ac-Stark effects. Using known $EF$ level energies, the level energies of $X(v=11, J=1,3-5)$ states are derived with accuracies of typically 0.002 cm$^{-1}$. These experimental values are in excellent agreement with, and are more accurate than the results obtained from the most advanced ab initio molecular theory calculations including relativistic and QED contributions.

physics.atom-ph↗

arXiv2016

Spectroscopy and perturbation analysis of the A$^1Π$(v=0) state of $^{13}$C$^{16}$O

The lowest $v=0$ level of the A$^1Π$, state of the $^{13}$C$^{16}$O isotopologue of carbon monoxide has been reinvestigated with a variety of high resolution spectroscopic techniques. The A$^1Π-$X$^1Σ^+(0,0)$ band has been studied by vacuum-ultraviolet Fourier-transform absorption spectroscopy, using the SOLEIL synchrotron as a radiation source. Spectra were obtained under quasi-static gas conditions at liquid-nitrogen temperature, room temperature and at an elevated temperature of 900 K, with absolute accuracies of 0.01$-$0.03 cm$^{-1}$. Two-photon Doppler-free laser spectroscopy has been applied to a limited number of transitions in the A$^1Π-$X$^1Σ^+(0,0)$ band, under collision-free circumstances of a molecular beam, yielding an absolute accuracy of 0.002 cm$^{-1}$. The third technique is high-resolution Fourier-transform emission spectroscopy in the visible region applied to the B$^1Σ^+-$A$^1Π(0,0)$ band in a gas discharge, at an absolute accuracy of up to 0.003 cm$^{-1}$. With these methods rotational levels of A$^1Π(0)$ could be studied in both parity components up to a rotational quantum number of $J=46$. The frequencies of 397 transitions were used to analyse the perturbations between the A$^1Π(0)$ level by vibrational levels of the D$^1\!Δ$, e$^3Σ^-$, d$^3\!Δ$, and a$'^3Σ^+$ states.

physics.atom-ph↗

arXiv2016

Constraint on a cosmological variation in the proton-to-electron mass ratio from electronic CO absorption

Carbon monoxide (CO) absorption in the sub-damped Lyman-$α$ absorber at redshift $z_{abs} \simeq 2.69$, toward the background quasar SDSS J123714.60+064759.5 (J1237+0647), was investigated for the first time in order to search for a possible variation of the proton-to-electron mass ratio, $μ$, over a cosmological time-scale. The observations were performed with the Very Large Telescope/Ultraviolet and Visual Echelle Spectrograph with a signal-to-noise ratio of 40 per 2.5 kms$^{-1}$ per pixel at $\sim 5000$ Å. Thirteen CO vibrational bands in this absorber are detected: the A$^{1}Π$ - X$^{1}Σ^{+}$ ($ν'$,0) for $ν' = 0 - 8$, B$^{1}Σ^{+}$ - X$^{1}Σ^{+}$ (0,0), C$^{1}Σ^{+}$ - X$^{1}Σ^{+}$ (0,0), and E$^{1}Π$ - X$^{1}Σ^{+}$ (0,0) singlet-singlet bands and the d$^{3}Δ$ - X$^{1}Σ^{+}$ (5,0) singlet-triplet band. An updated database including the most precise molecular inputs needed for a $μ$-variation analysis is presented for rotational levels $J = 0 - 5$, consisting of transition wavelengths, oscillator strengths, natural lifetime damping parameters, and sensitivity coefficients to a variation of the proton-to-electron mass ratio. A comprehensive fitting method was used to fit all the CO bands at once and an independent constraint of $Δμ/μ= (0.7 \pm 1.6_{stat} \pm 0.5_{syst}) \times 10^{-5}$ was derived from CO only. A combined analysis using both molecular hydrogen and CO in the same J1237+0647 absorber returned a final constraint on the relative variation of $Δμ/μ= (-5.6 \pm 5.6_{stat} \pm 3.1_{syst}) \times 10^{-6}$, which is consistent with no variation over a look-back time of $\sim 11.4$ Gyrs.

astro-ph.CO↗

arXiv2015

Spectroscopy and perturbation analysis of the CO A$^1Π-$X$^1Σ^+$ (2,0), (3,0) and (4,0) bands

The (2,0) (3,0) and (4,0) bands of the A$^1Π-$X$^1Σ^+$ system of $^{12}$C$^{16}$O have been re-investigated by high-resolution vacuum ultraviolet absorption spectroscopy. A VUV Fourier-transform spectrometer, illuminated by synchrotron radiation, was applied to record a jet-cooled spectrum, a room temperature static gas spectrum and a high temperature (900 K) quasi-static gas spectrum, resulting in absolute accuracies of 0.01$-$0.02 cm$^{-1}$ for the rotational line frequencies. Precise laser-based data were included in the analysis allowing for a highly accurate determination of band origins. Rotational levels up to $J=52$ were observed. The data were used to perform an improved analysis of the perturbations in the A$^1Π$, $v=2$, $v=3$, and $v=4$ levels by vibrational levels of the D$^1Δ$, I$^1Σ^-$, e$^3Σ^-$, d$^3Δ$, and a$'^3Σ^+$ states.

physics.atom-ph↗

arXiv2015

Test of quantum chemistry in vibrationally-hot hydrogen molecules

Precision measurements are performed on highly excited vibrational quantum states of molecular hydrogen. The $v=12, J=0-3$ rovibrational levels of H$_2$ ($X^1Σ_g^+$), lying only $2000$ cm$^{-1}$ below the first dissociation limit, were populated by photodissociation of H$_2$S and their level energies were accurately determined by two-photon Doppler-free spectroscopy. A comparison between the experimental results on $v=12$ level energies with the best \textit{ab initio} calculations shows good agreement, where the present experimental accuracy of $3.5 \times10^{-3}$ cm$^{-1}$ is more precise than theory, hence providing a gateway to further test theoretical advances in this benchmark quantum system.

physics.atom-ph↗

arXiv2015

Constraints on extra dimensions from precision molecular spectroscopy

Accurate investigations of quantum level energies in molecular systems are shown to provide a test ground to constrain the size of compactified extra dimensions. This is made possible by the recent progress in precision metrology with ultrastable lasers on energy levels in neutral molecular hydrogen (H$_2$, HD and D$_2$) and the molecular hydrogen ions (H$_2^+$, HD$^+$ and D$_2^+$). Comparisons between experiment and quantum electrodynamics calculations for these molecular systems can be interpreted in terms of probing large extra dimensions, under which conditions gravity will become much stronger. Molecules are a probe of space-time geometry at typical distances where chemical bonds are effective, i.e. at length scales of an Å. Constraints on compactification radii for extra dimensions are derived within the Arkani-Hamed-Dimopoulos-Dvali framework, while constraints for curvature or brane separation are derived within the Randall-Sundrum framework. Based on the molecular spectroscopy of D$_2$ molecules and HD$^+$ ions, the compactification size for seven extra dimensions (in connection to M-theory defined in 11 dimensions) of equal size is shown to be limited to $R_7 < 0.6 μ$m. While limits on compactification sizes of extra dimensions based on other branches of physics are compared, the prospect of further tightening constraints from the molecular method is discussed.

physics.atom-ph↗

arXiv2015

High-precision laser spectroscopy of the CO A$^1Π$ - X$^1Σ^+$ (2,0), (3,0) and (4,0) bands

High-precision two-photon Doppler-free frequency measurements have been performed on the CO A$^1Π$ - X$^1Σ^+$ fourth-positive system (2,0), (3,0), and (4,0) bands. Absolute frequencies of forty-three transitions, for rotational quantum numbers up to $J = 5$, have been determined at an accuracy of $1.6\times10^{-3}$ cm$^{-1}$, using advanced techniques of two-color 2+1' resonance-enhanced multi-photon ionization, Sagnac interferometry, frequency-chirp analysis on the laser pulses, and correction for AC-Stark shifts. The accurate transition frequencies of the CO A$^1Π$ - X$^1Σ^+$ system are of relevance for comparison with astronomical data in the search for possible drifts of fundamental constants in the early universe. The present accuracies in laboratory wavelengths of $Δλ/λ= 2 \times 10^{-8}$ may be considered exact for the purpose of such comparisons.

physics.atom-ph↗

arXiv2014

H$_2$ Lyman and Werner band lines and their sensitivity for a variation of the proton-electron mass ratio in the gravitational potential of white dwarfs

Recently an accurate analysis of absorption spectra of molecular hydrogen, observed with the Cosmic Origins Spectrograph aboard the Hubble Space Telescope, in the photosphere of white dwarf stars GD133 and GD29-38 was published in a Letter [Phys. Rev. Lett. 113, 123002 (2014)], yielding a constraint on a possible dependence of the proton-electron mass ratio on a gravitational field of strength 10,000 times that at the Earth's surface. In the present paper further details of that study are presented, in particular a re-evaluation of the spectrum of the $B^1Σ_u^+ - X^1Σ_g^+ (v',v'')$ Lyman bands relevant for the prevailing temperatures (12,000 - 14,000 K) of the photospheres. An emphasis is on the calculation of so-called $K_i$-coefficients, that represent the sensitivity of each individual line to a possible change in the proton-electron mass ratio. Such calculations were performed by semi-empirical methods and by ab initio methods providing accurate and consistent values. A full listing is provided for the molecular physics data on the Lyman bands (wavelengths $λ_i$, line oscillator strengths $f_i$, radiative damping rates $Γ_i$, and sensitivity coefficients $K_i$) as required for the analyses of H$_2$-spectra in hot dwarf stars. A similar listing of the molecular physics parameters for the $C^1Π_u - X^1Σ_g^+ (v',v'')$ Werner bands is provided for future use in the analysis of white dwarf spectra.

physics.atom-ph↗

arXiv2014

$B\,^1Σ^{+}_{u}$ and $EF\,^{1}Σ^{+}_{g}$ level energies of D$_{2}$

Accurate absolute level energies of the $B\,^1Σ^{+}_{u}$, $v=0-8, N$ and $EF\,^{1}Σ^{+}_{g}$, $v=0-21, N$ rovibrational quantum states of molecular deuterium are derived by combining results from a Doppler-free two-photon laser excitation study on several lines in the $EF\,{}^{1}Σ_{g}^{+}-X\,{}^{1}Σ_{g}^{+}$ (0,0) band, with results from a Fourier-transform spectroscopic emission study on a low-pressure hydrogen discharge. Level energy uncertainties as low as 0.0005 cm$^{-1}$ are obtained for some low-lying $E\,^{1}Σ^{+}_{g}$ inner-well rovibrational levels, while uncertainties for higher-lying rovibrational levels and those of the $F\,^{1}Σ^{+}_{g}$ outer-well states are nominally 0.005 cm$^{-1}$. Level energies of $B\,^1Σ^{+}_{u}$ rovibrational levels, for $v \leq 8$ and $N \leq 10$ are determined at an accuracy of 0.001 cm$^{-1}$. Computed wavelengths of D$_2$ Lyman transitions in the $B\,^1Σ^{+}_{u}-X\,^{1}Σ^{+}_{g}$ ($v,0$) bands are also tabulated for future applications.

physics.atom-ph↗

arXiv2014

Precision spectroscopy of the $X\,^{1}Σ_{g}^{+}, v=0\rightarrow 1$ ($J=0-2$) rovibrational splittings in H$_{2}$, HD and D$_{2}$

Accurate experimental values for the vibrational ground tone or fundamental vibrational energy splitting of H$_2$, HD, and D$_2$ are presented. Absolute accuracies of $2\times10^{-4}$ cm$^{-1}$ are obtained from Doppler-free laser spectroscopy applied in a collisionless environment. The vibrational splitting frequencies are derived from the combination difference between separate electronic excitations from the $X^{1}Σ_{g}^{+}, v=0, J$ and $v=1, J$ vibrational states to a common $EF^{1}Σ^{+}_{g}, v=0, J$ state. The present work on rotational quantum states $J=1,2$ extends the results reported by Dickenson et al. on $J=0$ [Phys. Rev. Lett. 110 (2013) 193601]. The experimental procedures leading to this high accuracy are discussed in detail. A comparison is made with full \emph{ab initio} calculations encompassing Born-Oppenheimer energies, adiabatic and non-adiabatic corrections, as well as relativistic corrections and QED-contributions. The present agreement between the experimental results and the calculations provides a stringent test on the application of quantum electrodynamics in molecules. Furthermore, the combined experimental-theoretical uncertainty can be interpreted to provide bounds to new interactions beyond the Standard Model of Physics or fifth forces between hadrons.

physics.atom-ph↗

arXiv2013

Novel techniques in VUV high-resolution spectroscopy

Novel VUV sources and techniques for VUV spectroscopy are reviewed. Laser-based VUV sources have been developed via non-linear upconversion of laser pulses in the nanosecond (ns), the picosecond (ps), and femtosecond (fs) domain, and are applied in high-resolution gas phase spectroscopic studies. While the ns and ps pulsed laser sources, at Fourier-transform limited bandwidths, are used in wavelength scanning spectroscopy, the fs laser source is used in a two-pulse time delayed mode. In addition a Fourier-transform spectrometer for high resolution gas-phase spectroscopic studies in the VUV is described, exhibiting the multiplex advantage to measure many resonances simultaneously.

physics.optics↗

arXiv2013

Bounds on fifth forces at the sub-Angstrom length scale

Constraints on a possible fifth-force interaction between hadrons are derived based on an analysis of results from laser precision frequency measurements of antiprotonic helium atoms, both $\bar{p}\,^{4}$He$^{+}$ and $\bar{p}\,^{3}$He$^{+}$ species, and from experiments on resonant formation rates of $ddμ^{+}$-ions in muon-catalyzed fusion processes. A comparison is made between accurate experimental data and first-principles theoretical descriptions of the exotic systems within a quantum electrodynamical framework. The agreement between theory and experiment sets limits on a possible additional hadron-hadron interaction written in the form of a Yukawa potential $V_5(r)=α_5 \exp(-r/λ)/r$, with $λ$ representing the characteristic length scale associated with the mass of a hypothetical force-carrying particle via $λ=\hbar/(m_5c)$. The laser spectroscopic data of antiprotonic helium set a constraint of $α_5/α_{EM} < 10^{-8}$ for $λ< 1$ Å, while the binding energy of the muonic molecular deuterium ion delivers a constraint of $α_5/α_{EM} \sim 10^{-5}$ for $λ< 0.05$ Å, where $α_{EM}$ represents the strength of the electromagnetic interaction or the fine structure constant.

hep-ph↗

arXiv2013

Bounds on fifth forces from precision measurements on molecules

Highly accurate results from frequency measurements on neutral hydrogen molecules H_2, HD and D_2 as well as the HD^+ ion can be interpreted in terms of constraints on possible fifth-force interactions. Where the hydrogen atom is a probe for yet unknown lepton-hadron interactions, and the helium atom is sensitive for lepton-lepton interactions, molecules open the domain to search for additional long-range hadron-hadron forces. First principles calculations in the framework of quantum electrodynamics have now advanced to the level that hydrogen molecules and hydrogen molecular ions have become calculable systems, making them a search-ground for fifth forces. Following a phenomenological treatment of unknown hadron-hadron interactions written in terms of a Yukawa potential of the form V_5(r)=βexp(-r/λ)/r current precision measurements on hydrogenic molecules yield a constraint β< 1 \times 10^{-7} eVÅfor long-range hadron-hadron interactions at typical force ranges commensurate with separations of a chemical bond, i.e. λ~1 Åand beyond.

physics.atom-ph↗

arXiv2013

Precision spectroscopy of high rotational states in H_2 investigated by Doppler-free two-photon laser spectroscopy in the EF^1Σ_g^+ - X^1Σ_g^+ system

Recently a high precision spectroscopic investigation of the EF^1Σ_g^+ - X^1Σ_g^+ system of molecular hydrogen was reported yielding information on QED and relativistic effects in a sequence of rotational quantum states in the X^1Σ^+_g$ ground state of the H_2 molecule [E.J. Salumbides et al., Phys. Rev. Lett. 107, 043005 (2011)]. The present paper presents a more detailed description of the methods and results. Furthermore, the paper serves as a stepping stone towards a continuation of the previous study by extending the known level structure of the EF^1Σ^+_g state to highly excited rovibrational levels through Doppler-free two photon spectroscopy. Based on combination differences between vibrational levels in the ground state, and between three rotational branches (O, Q and S branches) assignments of excited EF^1Σ^+_g levels, involving high vibrational and rotational quantum numbers, can be unambiguously made. For the higher EF^1Σ^+_g levels, where no combination differences are available, calculations were performed using the multi-channel quantum defect method, for a broad class of vibrational and rotational levels up to J=19. These predictions were used for assigning high-J EF-levels and are found to be accurate within 5 cm^-1.

physics.atm-clus↗

arXiv2012

The CO A-X System for Constraining Cosmological Drift of the Proton-Electron Mass Ratio

The $\textrm{A}^1Π-\textrm{X}^1Σ^+$ band system of carbon monoxide, which has been detected in six highly redshifted galaxies ($z=1.6-2.7$), is identified as a novel probe method to search for possible variations of the proton-electron mass ratio ($μ$) on cosmological time scales. Laboratory wavelengths of the spectral lines of the A-X ($v$,0) bands for $v=0-9$ have been determined at an accuracy of $Δλ/λ=1.5 \times 10^{-7}$ through VUV Fourier-transform absorption spectroscopy, providing a comprehensive and accurate zero-redshift data set. For the (0,0) and (1,0) bands, two-photon Doppler-free laser spectroscopy has been applied at the $3 \times 10^{-8}$ accuracy level, verifying the absorption data. Sensitivity coefficients $K_μ$ for a varying $μ$ have been calculated for the CO A-X bands, so that an operational method results to search for $μ$-variation.

physics.atom-ph↗

arXiv2012

High-resolution Fourier-transform XUV photoabsorption spectroscopy of 14N15N

The first comprehensive high-resolution photoabsorption spectrum of 14N15N has been recorded using the Fourier-transform spectrometer attached to the Desirs beamline at the Soleil synchrotron. Observations are made in the extreme ultraviolet (XUV) and span 100,000-109,000 cm-1 (100-91.7 nm). The observed absorption lines have been assigned to 25 bands and reduced to a set of transition energies, f values, and linewidths. This analysis has verified the predictions of a theoretical model of N2 that simulates its photoabsorption and photodissociation cross section by solution of an isotopomer independent formulation of the coupled-channel Schroedinger equation. The mass dependence of predissociation linewidths and oscillator strengths is clearly evident and many local perturbations of transition energies, strengths, and widths within individual rotational series have been observed.

physics.atm-clus↗

arXiv2011

QED effects in molecules: test on rotational quantum states of H$_2$

Quantum electrodynamic effects have been systematically tested in the progression of rotational quantum states in the $X ^{1}Σ_{g}^{+}, v=0$ vibronic ground state of molecular hydrogen. High-precision Doppler-free spectroscopy of the $EF ^{1}Σ_{g}^{+} - X ^{1}Σ_{g}^{+}$ (0,0) band was performed with 0.005 cm$^{-1}$ accuracy on rotationally-hot H$_2$ (with rotational quantum states J up to 16). QED and relativistic contributions to rotational level energies as high as 0.13 cm$^{-1}$ are extracted, and are in perfect agreement with recent calculations of QED and high-order relativistic effects for the H$_2$ ground state.

physics.atom-ph↗

arXiv2008

Frequency metrology on the 4s 2S1/2 - 4p 2P1/2 transition in the calcium ion for a comparison with quasar data

High accuracy frequency metrology on the 4s 2S1/2 - 4p 2P1/2 transition in calcium ions is performed using laser cooled and crystallized ions in a linear Paul trap. Calibration is performed with a frequency comb laser, resulting in a transition frequency of f=755222766.2(1.7) MHz. The accuracy presents an improvement of more than one order of magnitude, and will facilitate a comparison with quasar data in a search for a possible change of the fine structure constant on a cosmological time scale.

physics.atom-ph↗