Edcel John Salumbides

Vrije Universiteit Amsterdam | VU · Laser Centre

A laser system generating high-energy pulses at 2-µm wavelength with pulse widths tunable from 10–24 ns is described. It comprises an optical parametric oscillator that generates mJ-level signal seed radiation and an optical parametric amplifier that boosts the output to 800 mJ of combined signal and idler when pumped with 2 J pulses of 1064-nm las...

The technique of Noise-Immune Cavity Enhanced Optical Heterodyne Molecular Spectroscopy (NICE-OHMS) is employed to detect rovibrational transitions of H216O at wavelengths of 1.4 μm. This intracavity-saturation approach narrows down the typical Doppler-broadened linewidths of about 600 MHz to the sub-MHz domain. The locking of the spectroscopy lase...

The ionization energy of D2 has been determined experimentally from measurements involving two-photon Doppler-free vacuum-ultraviolet pulsed laser excitation and near-infrared continuous-wave laser excitation to yield EI(D2)=124745.393739(26) cm−1. From this value, the dissociation energy of D2 is deduced to be D0(D2)=36748.362282(26) cm−1, represe...

The ionization energy of D$_2$ has been determined experimentally from measurements involving two-photon Doppler-free vacuum-ultraviolet pulsed laser excitation and near-infrared continuous-wave laser excitation to yield $E_\mathrm{I}(\mathrm{D}_2)=124\,745.393\,739(26)$ \wn. From this value, the dissociation energy of D$_2$ is deduced to be $D_0$(...

Active frequency-chirp compensation for a narrowband pulsed Titanium-Sapphire laser system is demonstrated using an intra-cavity electro-optic modulator resulting in improved spectral resolution and stability. With referencing to an optical frequency comb and further residual frequency chirp detection from shot-to-shot measurements, the resulting l...

Quasi-bound resonances of H2 are produced via two-photon photolysis of H2S molecules as reactive intermediates or transition states and detected before decay of the parent molecule into three separate atoms. As was previously reported [K. F. Lai et al., Phys. Rev. Lett. 127, 183001 (2021)] four centrifugally bound quantum resonances with lifetimes...

Quasi-bound resonances of H$_2$ are produced via two-photon photolysis of H$_2$S molecules as reactive intermediates or transition states, and detected before decay of the parent molecule into three separate atoms. As was previously reported [K.F. Lai et al., Phys. Rev. Lett. 127, 183001 (2021)] four centrifugally bound quantum resonances with life...

Shape resonances in H2, produced as reaction intermediates in the photolysis of H2S precursor molecules, are measured in a half-collision approach. Before disintegrating into two ground state H atoms, the reaction is quenched by two-photon Doppler-free excitation to the F electronically excited state of H2. For J=13, 15, 17, 19, and 21, resonances...

Shape resonances in H$_2$, produced as reaction intermediates in the photolysis of H$_2$S precursor molecules, are measured in a half-collision approach. Before desintegrating into two ground state H atoms, the reaction is quenched by two-photon Doppler-free excitation to the F electronically excited state of H$_2$. For $J=13,15,17,19$ and 21, reso...

We present a parts-per-million test of quantum electrodynamics (QED) in the HD+ molecular hydrogen ion, improving on previous tests based on vibrational and rotational transitions by factors of 76 and 1.4, respectively. The test is performed following a unified statistical approach that also produces improved constraints on physics beyond the stand...

Taking advantage of the extreme absolute accuracy, sensitivity, and resolution of noise-immune-cavity-enhanced optical-heterodyne-molecular spectroscopy (NICE-OHMS), a variant of frequency-comb-assisted Lamb-dip saturation-spectroscopy techniques, the rotational quantum-level structure of both nuclear-spin isomers of H218O is established with an av...

Rovibrational quantum states in the X1Σ g + electronic ground state of H2 are prepared in the v = 13 vibrational level up to its highest bound rotational level J = 7, and in the highest bound vibrational level v = 14 (for J = 1) by two-photon photolysis of H2S. These states are laser-excited in a subsequent two-photon scheme into F1Σ g + outer well...

Rovibrational quantum states in the $X^1\Sigma_g^+$ electronic ground state of H$_2$ are prepared in the $v=13$ vibrational level up to its highest bound rotational level $J=7$, and in the highest bound vibrational level $v=14$ (for $J=1$) by two-photon photolysis of H$_2$S. These states are laser-excited in a subsequent two-photon scheme into $F^1...

Active frequency-chirp control for a narrowband pulsed titanium-sapphire laser oscillator-amplifier laser system is demonstrated using an intra-cavity electro-optic modulator, resulting in improved spectral resolution and stability. Beat-note measurements of its output to a continuous-wave laser locked to an optical frequency comb yields an Allan d...

Accurate Fourier-transform spectroscopic absorption measurements of vacuum ultraviolet transitions in atomic nitrogen and carbon were performed at the Soleil synchrotron. For 14 N, transitions from the 2s 2 2p 3 4 S 3/2 ground state and from the 2s 2 2p 3 2 P and 2 D metastable states were determined in the 95-124 nm range at an accuracy of 0.025 c...

Accurate Fourier-transform spectroscopic absorption measurements of vacuum ultraviolet transitions in atomic nitrogen and carbon were performed at the Soleil synchrotron. For $^{14}$N transitions from the $2s^22p^3\,^4$S$_{3/2}$ ground state and from the $2s^22p^3\,^2$P and $^2$D metastable states were determined in the $95 - 124$ nm range at an ac...

The $3p^{4}$ $^{3}$P$_{J}$ - $3p^{3}4p$ $^{3}$P$_{J}$ transition in the sulphur atom is investigated in a precision two-photon excitation scheme under Doppler-free and collision-free circumstances yielding an absolute accuracy of 0.0009 cm$^{-1}$, using a narrowband pulsed laser. This verifies and improves the level separations between amply studie...

A saturation spectroscopy measurement of the P(1) line of the (2−0) band in HD is performed in a sensitive cavity-enhanced optical setup involving frequency comb calibration. The spectral signature is that of a Lamb peak, in agreement with a density-matrix model description involving 9 hyperfine components and 16 crossover resonances of Λ type. Com...

A saturation spectroscopy measurement of the P(1) line of the ($2-0$) band in HD is performed in a sensitive cavity-enhanced optical setup involving frequency comb calibration. The spectral signature is that of a Lamb-peak, in agreement with a density-matrix model description involving 9 hyperfine components and 16 crossover resonances of $\Lambda$...

Frequency combs and cavity-enhanced optical techniques have revolutionized molecular spectroscopy: their combination allows recording saturated Doppler-free lines with ultrahigh precision. Network theory, based on the generalized Ritz principle, offers a powerful tool for the intelligent design and validation of such precision-spectroscopy experime...

High-resolution coherent Raman spectroscopic (CARS) measurements of all three tritium-containing molecular hydrogen isotopologues T2, DT and HT were performed to determine the ground electronic state fundamental Q-branch (v=0→1, ΔJ = 0) transition frequencies at accuracies of 0.0005 cm⁻¹. An over hundred-fold improvement in accuracy over previous e...

High-resolution coherent Raman spectroscopic measurements of all three tritium-containing molecular hydrogen isotopologues T$_2$, DT and HT were performed to determine the ground electronic state fundamental Q-branch ($v=0 \rightarrow 1, \Delta J = 0$) transition frequencies at accuracies of $0.0005$ cm$^{-1}$. An over hundred-fold improvement in a...

The saturation spectrum of the R(1) transition in the (2-0) band in HD is found to exhibit a composite line shape, involving a Lamb-dip and a Lamb-peak. We propose an explanation for such behavior based on the effects of cross-over resonances in the hyperfine substructure, which is made quantitative in a density-matrix calculation. This resolves an...

First-principles calculations are presented for fundamental vibrational splitting energies of tritium-bearing molecular hydrogen species with the improved treatment of the nonrelativistic, relativistic, and quantum electrodynamic energy contributions resulting in a total uncertainty of 0.00011 cm−1 for DT, or about a 100-times improvement over prev...

Bound and free quantum resonances of molecular hydrogen exhibiting wave-function density at large internuclear separation, R∼ 4–5 a.u., are excited via multi-step laser spectroscopy. Highly excited vibrational levels of H2 are prepared via two-photon UV-photolysis of H2S. Subsequent two-photon Doppler-free precision measurements are performed conne...

Nuclear-spin-symmetry conservation makes the observation of transitions between quantum states of ortho- and para-H2 extremely challenging. Consequently, the energy-level structure of H2 derived from experiment consists of two disjoint sets of level energies, one for para-H2 and the other for ortho-H2. We use a new measurement of the ionization ene...

The saturation spectrum of the R(1) transition in the (2-0) band in hydrogen deuteride (HD) is found to exhibit a composite line shape, involving a Lamb-dip and a Lamb-peak. We propose an explanation for such behavior based on the effects of crossover resonances in the hyperfine substructure, which is made quantitative in a density matrix calculati...

The dissociation energy of H2 represents a benchmark quantity to test the accuracy of first-principles calculations. We present a new measurement of the energy interval between the EFΣ1g+(v=0,N=1) state and the 54p11 Rydberg state of H2. When combined with previously determined intervals, this new measurement leads to an improved value of the disso...

The dissociation energy of H$_2$ represents a benchmark quantity to test the accuracy of first-principles calculations. We present a new measurement of the energy interval between the EF $^1\Sigma_g^+(v=0,N=1)$ state and the 54p1$_1$ Rydberg state of H$_2$. When combined with previously determined intervals, this new measurement leads to an improve...

Context. Absorption lines of H 2 and HD molecules observed at high redshift in the line of sight towards quasars are a test ground to search for variation of the proton-to-electron mass ratio μ . For this purpose, results from astronomical observations are compared with a compilation of molecular data of the highest accuracy, obtained in laboratory...

Context: Absorption lines of H$_2$ and HD molecules observed at high redshift in the line of sight towards quasars are a test ground to search for variation of the proton-to-electron mass ratio $\mu$. For this purpose results from astronomical observations are compared with a compilation of molecular data of the highest accuracy, obtained in labora...

We have reinvestigated the A$^1\Pi$$(v=0)$ level of $^{13}$C$^{18}$O\ using new high-resolution spectra obtained via multi-photon laser excitation as well as with synchrotron-based Fourier-transform absorption spectroscopy of the A$^1\Pi -\textrm{X}^1\Sigma^+$$(0, 0)$, e$^3\Sigma^--\textrm{X}^1\Sigma^+$$(1, 0)$, d$^3\Delta-\textrm{X}^1\Sigma^+$$(4,...

We have reinvestigated the A¹П(v = 0) level of ¹³C¹⁸O using new high-resolution spectra obtained via multi-photon laser excitation as well as with synchrotron-based Fourier-transform absorption spectroscopy of the A¹П−X¹∑⁺(0, 0), e³∑⁻- X¹∑⁺(1, 0), d³Δ−X¹∑⁺(4, 0), a'³∑⁺-X¹∑⁺(9, 0), and a¹П−X¹∑⁺(11, 0) bands. In addition, Fourier-transform emission s...

The ionization energy of ortho-H2 has been determined to be EIo(H2)/(hc)=124 357.238 062(25) cm−1 from measurements of the GK(1,1)−X(0,1) interval by Doppler-free, two-photon spectroscopy using a narrow band 179-nm laser source and the ionization energy of the GK(1,1) state by continuous-wave, near-infrared laser spectroscopy. EIo(H2) was used to d...

We have reinvestigated the A[chemical formula] level of 13C18O using new high-resolution spectra obtained via multi-photon laser excitation as well as with synchrotron-based Fourier-transform absorption spectroscopy of the A[chemical formula], e[chemical formula], d[chemical formula], a[chemical formula], and a[chemical formula] bands. In addition,...

The ionization energy of ortho-H$_2$ has been determined to be $E^\mathrm{o}_\mathrm{I}(\mathrm{H}_2)/(hc)=124\,357.238\,062(25)$ cm$^{-1}$ from measurements of the GK(1,1)--X(0,1) interval by Doppler-free two-photon spectroscopy using a narrow band 179-nm laser source and the ionization energy of the GK(1,1) state by continuous-wave near-infrared...

The hydrogen molecule has become a test ground for quantum electrodynamical calculations in molecules. Expanding beyond studies on stable hydrogenic species to the heavier radioactive tritium-bearing molecules, we report on a measurement of the fundamental T$_2$ vibrational splitting $(v= 0 \rightarrow 1)$ for $J=0-5$ rotational levels. Precision f...

Molecular hydrogen and its isotopic and ionic species are benchmark systems for testing quantum chemical theory. Advances in molecular energy structure calculations enable the experimental verification of quantum electrodynamics and potentially a determination of the proton charge radius from H2 spectroscopy. We measure the ground state energy in o...

Accurate \( E{F}^1{\varSigma}_g^{+}-{X}^1{\varSigma}_g^{+} \) 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 \( {\mathrm{H}}_2^{\ast } \)...

Weak transitions in the (2,0) overtone band of the HD molecule at $\lambda = 1.38 \, \mu$m were measured in saturated absorption using the technique of noise-immune cavity-enhanced optical heterodyne molecular spectroscopy. Narrow Doppler-free lines were interrogated with a spectroscopy laser locked to a frequency comb laser referenced to an atomic...

Molecular hydrogen is a benchmark system for bound state quantum calculation and tests of quantum electrodynamical effects. While spectroscopic measurements on the stable species have progressively improved over the years, high resolution studies on the radioactive isotopologues $\rm{T_2}$, $\rm{HT}$ and $\rm{DT}$ have been limited. Here we present...

The A¹Π(v = 0) level of ¹²C¹⁸O has been reinvestigated using three different high-resolution spectroscopic methods: (1) 2 + 1′ resonance-enhanced multiphoton ionisation of the A¹Π − X¹Σ⁺(0, 0) band using narrowband lasers in a Doppler-free geometry; (2) Fourier-transform emission spectroscopy in the visible range probing the B¹Σ⁺ − A¹Π(0, 0) band i...

The high-resolution B1Σ+ → A1Π (0, 0) and (0, 3) emission bands of the less-abundant 13C17O isotopologue have been investigated by Fourier-transform spectroscopy in the visible region using a Bruker IFS 125HR spectrometer at an accuracy 0.003 cm-1. These spectra are combined with high-resolution photoabsorption measurements of the 13C17O B1Σ+ ← X1Σ...

The high-resolution B1Σ+ → A1Π (0, 0) and (0, 3) emission bands of the less-abundant 13C17O isotopologue have been investigated by Fourier-transform spectroscopy in the visible region using a Bruker IFS 125HR spectrometer at an accuracy 0.003 cm-1. These spectra are combined with high-resolution photoabsorption measurements of the 13C17O B1Σ+ ← X1Σ...

The high-resolution B[superscript 1]Σ[superscript +]→A[superscript 1]Π (0, 0) and (0, 3) emission bands of the less-abundant [superscript 13]C[superscript 17]O isotopologue have been investigated by Fourier-transform spectroscopy in the visible region using a Bruker IFS 125HR spectrometer at an accuracy 0.003 cm[superscript -1]. These spectra are c...

Accurate $EF{}^1\Sigma^+_g-X{}^1\Sigma^+_g$ 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...

The lowest $v=0$ level of the A$^1\Pi$, state of the $^{13}$C$^{16}$O isotopologue of carbon monoxide has been reinvestigated with a variety of high resolution spectroscopic techniques. The A$^1\Pi-$X$^1\Sigma^+(0,0)$ band has been studied by vacuum-ultraviolet Fourier-transform absorption spectroscopy, using the SOLEIL synchrotron as a radiation s...

Electronic spectra of C₆H are measured in the 18950–21100 cm⁻¹ domain using cavity ring-down spectroscopy of a supersonically expanding hydrocarbon plasma. In total, 19 (sub)bands of C₆H are presented, all probing the vibrational manifold of the B²Π electronically excited state. The assignments are guided by electronic spectra available from matrix...

Carbon monoxide (CO) absorption in the sub-damped Lyman-$\alpha$ 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, $\mu$, over a cosmological time-scale. The observations...

High-accuracy dispersive optical spectroscopy measurements in the visible (VIS) region have been performed on the less-abundant 12C17O isotopologue, observing high-resolution emission bands of the B1Σ+ (υ = 0) → A1Π (υ = 3, 4, and 5) Ångström system. These are combined with high-resolution photoabsorption measurements of the 12C17O B1Σ+ (υ = 0) ← X...

High-accuracy dispersive optical spectroscopy measurements in the visible (VIS) region have been performed on the less-abundant [superscript 12]C[superscript 17]O isotopologue, observing high-resolution emission bands of the B[superscript 1]Σ+ (υ = 0) → A[superscript 1]Π (υ = 3, 4, and 5) Ångström system. These are combined with high-resolution pho...

The (2,0) (3,0) and (4,0) bands of the A1Π −X1Σ+ system of 12C16O have been re-investigated by high-resolution vacuum ultraviolet absorption spectroscopy. A vacuum ultraviolet Fourier-transform spectrometer, illuminated by synchrotron radiation, was applied to record a jet-cooled spectrum, a room temperature static gas spectrum and a high-temperatu...

An overview is presented of the H$_2$ quasar absorption method to search for a possible variation of the proton--electron mass ratio $\mu=m_p/m_e$ on a cosmological time scale. Details of the analysis of astronomical spectra, obtained with large 8--10 m class optical telescopes, equipped with high-resolution echelle grating based spectrographs, are...

Spectroscopy of hydrogen can be used for a search into physics beyond the Standard Model. Differences between the absorption spectra of H$_2$ as observed at high redshift and those measured in the laboratory can be interpreted in terms of possible variations of the proton-electron mass ratio. Investigation of some ten of such absorbers in the redsh...

The (2,0) (3,0) and (4,0) bands of the A$^1\Pi-$X$^1\Sigma^+$ 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 t...

Precision measurements are performed on highly excited vibrational quantum states of molecular hydrogen. The $v=12, J=0-3$ rovibrational levels of H$_2$ ($X^1\Sigma_g^+$), 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 Do...