Fourier-transform spectroscopy of HD in the vacuum ultraviolet at λ = 87–112 nm

Abstract

Absorption spectroscopy in the vacuum ultraviolet (VUV) domain was performed on the hydrogen-deuteride molecule with a novel Fourier-Transform spectrometer based upon wavefront division interferometry. This unique instrument, which is a permanent endstation of the undulator-based beamline DESIRS on the synchrotron SOLEIL facility, opens the way to Fourier-Transform spectroscopy in the VUV range. The HD spectral lines in the Lyman and Werner bands were recorded in the 87-112 nm range from a quasi-static gas sample in a windowless configuration and with a Doppler-limited resolution. Line positions of some 268 transitions in the B 1 Σ + u (v ′ = 0 − 30) ← X 1 Σ + g (v ′′ = 0) Lyman bands and 141 transitions in the C 1 Πu(v ′ = 0 − 10) ← X 1 Σ + g (v ′′ = 0) Werner bands were deduced with uncertainties of 0.04 cm −1 (1σ) which correspond to ∆λ/λ ∼ 4 × 10 −7. This extensive laboratory database is of relevance for comparison with astronomical observations of H 2 and HD spectra from highly redshifted objects, with the goal of extracting a possible variation of the proton-to-electron mass ratio (µ = mp/me) on a cosmological time scale. For this reason also calculations of the so-called sensitivity coefficients K i were performed in order to allow for deducing constraints on ∆µ/µ. The K i coefficients, associated with the line shift that each spectral line undergoes as a result of a varying value for µ, were derived from calculations as a function of µ solving the Schrödinger equation using ab initio potentials.

VUV Fourier-transform absorption study of the Lyman and Werner bands in D2

“…This absorption facility was also used in a previous investigation on the Lyman and Werner bands of the HD molecule. 30 In the present study, a third type of measurement is performed in addition to the gas cell setup with two different coolants. The FTS is used to record absorption spectra from a D 2 molecular gas jet for the first time.…”

“…27,28,30 Due to small alignment offsets of the heliumneon laser and the VUV beam relative directions, that may vary from run to run, the absolute calibration also varies for different runs, and can be improved upon by anchoring the spectra to several accurately known D 2 lines in addition to a few Xe and Kr lines that occur in the spectra, finding their origin in the gas filter used for attenuating the harmonics at short wavelengths produced in the undulator. Some 39 lines belonging to the…”

VUV Spectroscopic Study of theD1ΠuState of Molecular Deuterium

“…For a detailed description of the FT-spectrometer we refer to Refs. [17,18,26]. For the broad, predissociated transitions (v 4) the cell-configuration was used.…”

High-resolution Fourier-transform extreme ultraviolet photoabsorption spectroscopy of 14N15N

“…[49][50][51] and general properties of ultraviolet interferometry 48 are given in detail elsewhere and are only briefly described here. The spectrometer is based upon a wave-front-division interferometer and may be operated at XUV and VUV wavelengths.…”