M. Niu

CO A-X system for constraining cosmological drift of the proton-electron mass ratio

Author Institution: Department of Physics and Astronomy, and LaserLaB, VU University, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands; Synchrotron Soleil, Orme des Merisiers, St Aubin BP 48, 91192, GIF sur Yvette cedex, France; Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA; Department of Physics and Astronomy, and LaserLaB, VU University, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands

High resolution spectroscopy and perturbation analysis of the CO A1Π −X1Σ+ (0,0) and (1,0) bands

The two lowest-v′ (0,0) and (1,0) bands of the A1Π −X1Σ+ system of 12C16O have been investigated by two high-resolution spectroscopic methods. A vacuum ultraviolet Fourier-transform spectrometer, illuminated by synchrotron radiation, was applied to record a jet-cooled spectrum and a room temperature static gas spectrum, resulting in absolute accuracies of 0.01−0.02 cm−1. In addition two-photon Doppler-free laser spectroscopy has been applied to a limited number of rotational lines, resulting in an accuracy of 0.002 cm−1. The data were used to perform an improved analysis of the perturbations in the A1Π, v = 0 and v = 1 levels by vibrational levels in the D1Δ, I1Σ−, e3Σ−, d3Δ. and a′3Σ+ states.

Spectroscopy and perturbation analysis of the CO A

ABSTRACT 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-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 A1Π, v = 2, v = 3 and v = 4 levels by vibrational levels of the D1Δ, I1Σ−, e3Σ−, d3Δ and a′3Σ+ states.

^1\Pi-

Precision measurements are performed on highly excited vibrational quantum states of molecular hydrogen. The v = 12, J = 0 - 3 rovibrational levels of H2 (X(1)Σg (+)), lying only 2000 cm(-1) below the first dissociation limit, were populated by photodissociation of H2S 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 ab initio calculations shows a good agreement, where the present experimental accuracy of 3.5 × 10(-3) cm(-1) is more precise than theory, hence providing a gateway to further test theoretical advances in this benchmark quantum system.

X

Accurate experimental values for the vibrational ground tone or fundamental vibrational energy splitting of H2, HD, and D2 are presented. Absolute accuracies of 2×10 −4 cm 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 XΣg , v = 0, J and v = 1, J vibrational states to a common EF Σg , 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 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.

^1\Sigma^+

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) Angstrom system. These are combined with high-resolution photoabsorption measurements of the 12C17O B1Σ+ (υ = 0) ← X1Σ+ (υ = 0) and C1Σ+ (υ = 0) ← X1Σ+ (υ = 0) Hopfield–Birge bands recorded with the vacuum-ultraviolet (VUV) Fourier transform spectrometer, installed on the DESIRS beamline at the SOLEIL synchrotron. The frequencies of 429 observed transitions have been determined in the 15 100–18 400 cm−1 and 86 900–92 100 cm−1 regions with an absolute accuracy of up to 0.003 cm−1 and 0.005 cm−1 for the B–A, and B–X, C–X systems, respectively. These new experimental data were combined with data from the previously analysed C → A and B → A systems. The comprehensive data set, 982 spectral lines belonging to 12 bands, was included in a deperturbation analysis of the A1Π, υ = 1–5 levels of 12C17O, taking into account interactions with levels in the d3Δi, e3Σ−, a′3Σ+, I1Σ− and D1Δ states. The A1Π and perturber states were described in terms of a set of deperturbed molecular constants, spin–orbit and L-uncoupling interaction parameters, equilibrium constants, 309 term values, as well as isotopologue-independent spin–orbit and rotation-electronic perturbation parameters.

(2,0), (3,0) and (4,0) bands

ABSTRACT The lowest v = 0 level of the A1Π state of the 13C16O isotopologue of carbon monoxide has been reinvestigated with a variety of high-resolution spectroscopic techniques. The A1Π −X1Σ+(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 A1Π −X1Σ+(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 B1Σ+ −A1Π(0, 0) band in a gas discharge, at an absolute accuracy of up to 0.003 cm−1. With these methods, rotational levels of A1Π (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 A1Π(0) level by vibrational levels of the D1Δ, e3Σ−, d3Δ, and a′3Σ+ states.

Communication: Test of quantum chemistry in vibrationally hot hydrogen molecules.

Recently a high precision spectroscopic investigation of the EF1 Sigma(+)(g)-X-1 Sigma(+)(g) system of molecular hydrogen was reported yielding information on QED and relativistic effects in a sequence of rotational quantum states in the X-1 Sigma(+)(g) ground state of the H-2 molecule [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 EF1 Sigma(+)(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 EF1 Sigma(+)(g) levels, involving high vibrational and rotational quantum numbers, can be unambiguously made. For the higher EF1 Sigma(+)(g) levels, where no combination differences are available, calculations were performed using the multichannel 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).

VUV-synchrotron absorption studies of N-2 and CO at 900 K

ABSTRACT 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 in a discharge; (3) Fourier-transform absorption spectroscopy in the vacuum-ultraviolet range measuring the A1Π − X1Σ+(0, 0) and B1Σ+ − X1Σ+(0, 0) bands at multiple temperatures ranging from 90 to 900 K. An effective-Hamiltonian analysis of A1Π, v = 0 levels was performed up to J = 44 which quantitatively addresses perturbations by the e 3Σ−(v = 1), d3Δ(v = 4), a′3Σ+(v = 9), D 1Δ(v = 0), and I 1Σ−(v = 0, 1) levels.