A near infrared line list for \NH: Analysis of a Kitt Peak spectrum after 35 years

A Fourier Transform (FT) absorption spectrum of room temperature NH3 in the region 7400 - 8600 cm-1 is analysed using a variational line list and ground state energies determined using the MARVEL procedure. The spectrum was measured by Dr Catherine de Bergh in 1980 and is available from the Kitt Peak data center. The centers and intensities of 8468 ammonia lines were retrieved using a multiline fitting procedure. 2474 lines are assigned to 21 bands providing 1692 experimental energies in the range 7000 - 9000 cm-1. The spectrum was assigned by the joint use of the BYTe variational line list and combination differences. The assignments and experimental energies presented in this work are the first for ammonia in the region 7400 - 8600 cm-1, considerably extending the range of known vibrational-excited statesComment: 27 pages, 6 table, 5 figures. Accepted for publication in Journal of Molecular Spectroscop

First observation of electric-quadrupole infrared transitions in water vapour

Molecular absorption of infrared radiation is generally due to ro-vibrational electric-dipole transitions. Electric-quadrupole transitions may still occur, but they are typically a million times weaker than electric-dipole transitions, rendering their observation extremely challenging. In polyatomic or polar diatomic molecules, ro-vibrational quadrupole transitions have never been observed. Here, we report the first direct detection of quadrupole transitions in water vapor. The detected quadrupole lines have intensity largely above the standard dipole intensity cut-off of spectroscopic databases and thus are important for accurate atmospheric and astronomical remote sensing

High sensitivity Cavity Ring Down spectroscopy of 18O enriched carbon dioxide between 5850 and 7000 cm-1: Part III-Analysis and theoretical modeling of the 12C17O2, 16O12C17O, 17O12C18O, 16O13C17O and 17O13C18O spectra

More than 19,700 transitions belonging to 11 isotopologues of carbon dioxide have been assigned in the room temperature absorption spectrum of highly 18O enriched carbon dioxide recorded by very high sensitivity CW-Cavity Ring Down spectroscopy between 5851 and 6990 cm-1 (1.71-1.43 \mum). This third and last report is devoted to the analysis of the bands of five 17O containing isotopologues present at very low concentration in the studied spectra: 16O12C17O, 17O12C18O, 16O13C17O, 17O13C18O and 12C17O2 (627, 728, 637, 738 and 727 in short hand notation). On the basis of the predictions of effective Hamiltonian models, a total of 1759, 1786, 335, 273 and 551 transitions belonging to 24, 24, 5, 4 and 7 bands were rovibrationally assigned for 627, 728, 637, 738 and 727, respectively. For comparison, only five bands were previously measured in the region for the 728 species. All the identified bands belong to the \deltaP=8 and 9 series of transitions, where P=2V1+V2+3V3 is the polyad number (Vi are vibrational quantum numbers). The band-by-band analysis has allowed deriving accurate spectroscopic parameters of 61 bands from a fit of the measured line positions. Two interpolyad resonance perturbations were identified

COMB-ASSISTED CAVITY RING DOWN SPECTROSCOPY OF 17O ENRICHED WATER BETWEEN 7443 AND 7921 CM−1

The room temperature absorption spectrum of water vapour highly enriched in chem{^{17}O} has been recorded by Cavity Ring Down Spectroscopy (CRDS) between 7443 and 7921 wn. Three series of recordings were performed with pressure values around 0.1, 1 and 10 Torr. The frequency calibration of the present spectra benefited of the combination of the CRDS spectrometer to a self-referenced frequency comb. The resulting CRD spectrometer combines excellent frequency accuracy over a broad spectral region with a high sensitivity (Noise Equivalent Absorption, $alpha_{min}sim10^{-11}-10^{-10}$ wn). _x000d_ The investigated spectral region corresponds to the high energy range of the first hexade. The assignments were performed using known experimental energy levels as well as calculated line lists based on the results of Partridge and Schwenke. Overall about 4150 lines were measured and assigned to 4670 transitions of six water isotopologues (chem{H_2^{16}O}, chem{H_2^{17}O}, chem{H_2^{18}O}, chem{HD^{16}O}, chem{HD^{17}O} and chem{HD^{18}O}). Their intensities span six orders of magnitude from 10$^{-28}$ to 10$^{-22}$ cm/molecule. Most of the new results concern the chem{H_2^{17}O} and chem{HD^{17}O} isotopologues for which about 1600 and 400 transitions were assigned leading to the determination of 329 and 207 new energy levels, respectively. For comparison only about 300 and four transitions of chem{H_2^{17}O} and chem{HD^{17}O} were previously known in the region, respectively._x000d_ By comparison to highly accurate chem{H_2^{16}O} line positions available in the literature, the average accuracy on our line centers is checked to be on the order of 3 MHz (10$^{-4}$ wn) or better for unblended lines. This small uncertainty represents a significant improvement of the line center determination of many chem{H_2^{16}O} lines in the considered region

ACCURATE LASER MEASUREMENTS OF THE WATER VAPOR SELF-CONTINUUM ABSORPTION IN FOUR NEAR INFRARED ATMOSPHERIC WINDOWS. A TEST OF THE MT_CKD MODEL.

The semi empirical MT_CKD model of the absorption continuum of water vapor is widely used in atmospheric radiative transfer codes of the atmosphere of Earth and exoplanets but lacks of experimental validation in the atmospheric windows. Recent laboratory measurements by Fourier transform Spectroscopy have led to self-continuum cross-sections much larger than the MT_CKD values in the near infrared transparency windows. _x000d_ In the present work, we report on accurate water vapor absorption continuum measurements by Cavity Ring Down Spectroscopy (CRDS) and Optical-Feedback-Cavity Enhanced Laser Spectroscopy (OF-CEAS) at selected spectral points of the transparency windows centered around 4.0, 2.1 and 1.25 $mu$m. The temperature dependence of the absorption continuum at 4.38 $mu$m and 3.32 $mu$m is measured in the 23-39 $^{circ}$C range. The self-continuum water vapor absorption is derived either from the baseline variation of spectra recorded for a series of pressure values over a small spectral interval or from baseline monitoring at fixed laser frequency, during pressure ramps. In order to avoid possible bias approaching the water saturation pressure, the maximum pressure value was limited to about 16 Torr, corresponding to a 75% humidity rate._x000d_ After subtraction of the local water monomer lines contribution, self-continuum cross-sections, C$_{S}$, were determined with a few % accuracy from the pressure squared dependence of the spectra base line level. _x000d_ Together with our previous CRDS and OF-CEAS measurements in the 2.1 and 1.6 $mu$m windows, the derived water vapor self-continuum provides a unique set of water vapor self-continuum cross-sections for a test of the MT_CKD model in four transparency windows. Although showing some important deviations of the absolute values (up to a factor of 4 at the center of the 2.1 $mu$m window), our accurate measurements validate the overall frequency dependence of the MT_CKD2.8 model. _x000d

AN EMPIRICAL SPECTROSCOPIC DATABASE FOR ACETYLENE IN THE REGIONS OF 5850-9415 CM−1

Six studies have been recently devoted to a systematic analysis of the high-resolution near infrared absorption spectrum of acetylene recorded by Cavity Ring Down spectroscopy (CRDS) in Grenoble and by Fourier-transform spectroscopy (FTS) in Brussels and Hefei. On the basis of these works, in the present contribution, we construct an empirical database for acetylene in the 5850 - 9415 $wn$ region excluding the 6341-7000 $wn$ interval corresponding to the very strong nub{1}+ nub{3} manifold. The database gathers and extends information included in our CRDS and FTS studies. In particular, the intensities of about 1700 lines measured by CRDS in the 7244-7920 $wn$ are reported for the first time together with those of several bands of $^{12}$C$^{13}$CH$_{2}$ present in natural isotopic abundance in the acetylene sample. _x000d_ The Herman-Wallis coefficients of most of the bands are derived from a fit of the measured intensity values. A recommended line list is provided with positions calculated using empirical spectroscopic parameters of the lower and upper energy vibrational levels and intensities calculated using the derived Herman-Wallis coefficients. This approach allows completing the experimental list by adding missing lines and improving poorly determined positions and intensities. As a result the constructed line list includes a total of 10973 lines belonging to 146 bands of $^{12}$C$_{2}$H$_{2}$ and 29 bands of $^{12}$C$^{13}$CH$_{2}$. For comparison the HITRAN2012 database in the same region includes 869 lines of 14 bands, all belonging to $^{12}$C$_{2}$H$_{2}$. Our weakest lines have an intensity on the order of 10$^{-29}$ cm/molecule,about three orders of magnitude smaller than the HITRAN intensity cut off. Line profile parameters are added to the line list which is provided in HITRAN format._x000d_ The comparison to the HITRAN2012 line list or to results obtained using the global effective operator approach is discussed in terms of completeness and accuracy._x000d

Stark deceleration of lithium hydride molecules

We describe the production of cold, slow-moving LiH molecules. The molecules are produced in the ground state using laser ablation and supersonic expansion, and 68% of the population is transferred to the rotationally excited state using narrowband radiation at the rotational frequency of 444GHz. The molecules are then decelerated from 420m/s to 53m/s using a 100 stage Stark decelerator. We demonstrate and compare two different deceleration modes, one where every stage is used for deceleration, and another where every third stage decelerates and the intervening stages are used to focus the molecules more effectively. We compare our experimental data to the results of simulations and find good agreement. These simulations include the velocity dependence of the detection efficiency and the probability of transitions between the weak-field seeking and strong-field seeking quantum states. Together, the experimental and simulated data provide information about the spatial extent of the source of molecules. We consider the prospects for future trapping and sympathetic cooling experiments.Comment: 14 pages, 6 figures; minor revisions following referee suggestion

Electric quadrupole transitions in carbon dioxide

Recent advances in the high sensitivity spectroscopy have made it possible, in combination with accurate theoretical predictions, to observe for the first time very weak electric quadrupole transitions in a polar polyatomic molecule of water. Here we present accurate theoretical predictions of the complete quadrupole ro-vibrational spectrum of a non-polar molecule CO$_2$, important in atmospheric and astrophysical applications. Our predictions are validated by recent cavity enhanced absorption spectroscopy measurements and are used to assign few weak features in the recent ExoMars ACS MIR spectroscopic observations of the martian atmosphere. Predicted quadrupole transitions appear in some of the mid-infrared CO$_2$ and water vapor transparency regions, making them important for detection and characterization of the minor absorbers in water- and CO$_2$-rich environments, such as present in the atmospheres of Earth, Venus and Mars

Communication: Saturated CO 2

International audienc

Towards magnetic slowing of atoms and molecules

We outline a method to slow paramagnetic atoms or molecules using pulsed magnetic fields. We also discuss the possibility of producing trapped particles by adiabatic deceleration of a magnetic trap. We present numerical simulation results for the slowing and trapping of molecular oxygen