scholarly journals Rotational spectroscopy of the HCCO and DCCO radicals in the millimeter and submillimeter range

2019 ◽  
Vol 621 ◽  
pp. A111 ◽  
Author(s):  
J. Chantzos ◽  
S. Spezzano ◽  
C. Endres ◽  
L. Bizzocchi ◽  
V. Lattanzi ◽  
...  
Keyword(s):  
Submillimeter Range ◽  
Data Set ◽  
Rotational Spectra ◽  
Dark Clouds ◽  
Chemical Models ◽  
Distortion Parameters ◽  
First Time ◽  
Low Density Plasma ◽  
Hydrocarbon Chemistry

Context. The ketenyl radical HCCO has recently been detected in the interstellar medium (ISM) for the first time. Further astronomical detections of HCCO will help us understand its gas-grain chemistry, and subsequently revise the oxygen-bearing chemistry towards dark clouds. Moreover, its deuterated counterpart DCCO has never been observed in the ISM. A broad spectroscopic investigation is still lacking for both HCCO and DCCO, although they exhibit a significant astrophysical relevance. Aims. In this work we aim to measure the pure rotational spectra of the ground state of HCCO and DCCO in the millimeter and submillimeter region, considerably extending the frequency range covered by previous studies. Methods. The spectral acquisition was performed using a frequency-modulation absorption spectrometer between 170 and 650 GHz. The radicals were produced in a low-density plasma generated from a select mixture of gaseous precursors. We were able to detect and assign more than 100 rotational lines for each isotopolog. Results. The new lines have significantly enhanced the previous data set allowing the determination of highly precise rotational and centrifugal distortion parameters. In our analysis we took into account the interaction between the ground electronic state and a low-lying excited state (Renner–Teller pair) which enables the prediction and assignment of rotational transitions with Ka up to 4. Conclusions. The present set of spectroscopic parameters provides highly accurate, millimeter, and submillimeter rest-frequencies of HCCO and DCCO for future astronomical observations. We also show that towards the pre-stellar core L1544, ketenyl peaks in the region where c-C3H2 peaks, suggesting that HCCO follows a predominant hydrocarbon chemistry, as already proposed by recent gas-grain chemical models.

Rotational Spectra of Phosphorus Monosulfide up to 1 THz

1999 ◽  
Vol 54 (2) ◽  
pp. 137-145
Author(s):  
H. Klein ◽  
E. Klisch ◽  
G. Winnewisser
Keyword(s):  
Submillimeter Wave ◽  
Rotational Spectrum ◽  
Data Set ◽  
Rotational Spectra ◽  
Quantum Numbers ◽  
Hyperfine Constants ◽  
Vibrational Ground State ◽  
Structure Constants ◽  
First Time ◽  
Rotation Constant

Abstract The submillimeter-wave rotational spectrum of the PS radical in the electronic and vibrational ground state (X2 ΠI/2 , X2Π3/2) was recorded with the Cologne terahertz spectrometer in the fre-quency region between 540 GHz and 1.07 THz, covering rotational quantum numbers from J = 30.5 to 60.5. The PS radical has been produced by discharging PSCl3 buffered with Ar. For all transitions the Λ-doubling was resolved for both the 2ΠI/2 and 2Π3/2 states. For some transitions with ΔF = 0 the hyperfine structure (hfs) caused by the P-atom could partially be resolved even for rather high J values. Analysis of the complete rotational data set of PS allows the derivation of a full set of molecular parameters, including the rotational constants B, D, H, the fine-structure constants A,γ , Dγ , the parameters for the Λ-doubling p, Dp , q, and the magnetic hyperfine constants a, b, c, d, CI. All parameters have been determined, whereby a, c, and the nuclear spin rotation-constant CI were obtained for the first time.

First Determination of the Proton's Weak Charge

2015 ◽  
Vol 8 (3) ◽  
Author(s):  
Shelley A. Page
Keyword(s):  
Standard Model ◽  
High Precision ◽  
Standard Model Prediction ◽  
Data Set ◽  
Weak Charge ◽  
Newport News ◽  
The Standard Model ◽  
First Results ◽  
First Time

The weak charge of the proton has been determined for the first time via a high precision electron-proton scattering experiment, Qweak, carried out at Jefferson Laboratory (JLab) in Newport News, USA. The weak charge is a basic property in subatomic physics, analogous to electric charge. The Standard Model makes a prediction for the weak charges of protons and other particles. First results described here are based on an initial 4% of the data set reported in 20131, with the ultimate goal of the experiment being a high precision Standard Model test conducted with the full Qweak data set. These initial results are consistent with the Standard Model prediction; they serve as an important first determination of the proton’s weak charge and a proof of principle that the ultimate goals are within reach.

scholarly journals Characterizing the chemical pathways for water formation – a deep search for hydrogen peroxide

2014 ◽  
Vol 168 ◽  
pp. 349-367 ◽  
Author(s):  
Bérengère Parise ◽  
Per Bergman ◽  
Karl Menten
Keyword(s):  
Hydrogen Peroxide ◽  
Dark Clouds ◽  
Chemical Models ◽  
Upper Limits ◽  
Low Mass ◽  
And Shifts ◽  
First Time ◽  
Infrared Dark Clouds ◽  
Very High ◽  
High Column

In 2011, hydrogen peroxide (HOOH) was observed for the first time outside the solar system (Bergman et al., Astron. Astrophys., 2011, 531, L8). This detection appeared a posteriori to be quite natural, as HOOH is an intermediate product in the formation of water on the surface of dust grains. Following up on this detection, we present a search for HOOH in a diverse sample of sources in different environments, including low-mass protostars and regions with very high column densities, such as Infrared Dark Clouds (IRDCs). We do not detect the molecule in any other source than Oph A, and derive 3σ upper limits for the abundance of HOOH relative to H2 lower than that in Oph A for most sources. This result sheds a different light on our understanding of the detection of HOOH in Oph A, and shifts the question of why this source seems to be special. Therefore we rediscuss the detection of HOOH in Oph A, as well as the implications of the low abundance of HOOH, and its similarity with the case of O2. Our chemical models show that the production of HOOH is extremely sensitive to temperature, and is favored only in the range 20–30 K. The relatively high abundance of HOOH observed in Oph A suggests that the bulk of the material lies at a temperature in the range 20–30 K.

scholarly journals Determination of Rotational Parameters of CH3CN, CD3CN and their Different Isotopic Species in the Ground and v4= 1 States

2009 ◽  
Vol 6 (2) ◽  
pp. 577-593
Author(s):  
Masoud Motamedi ◽  
Parinaz Moradi
Keyword(s):  
Millimeter Wave ◽  
Rotational Spectra ◽  
Isotopic Species ◽  
Symmetric Top Molecules ◽  
First Time

The millimeter-wave rotational spectra of the symmetric top molecules CH3CN,13CH3CN, CH313CN, CH3C15N, CD3CN ,13CD3CN, CD313CN and CD3C15N have been investigated again in their ground and v4= 1 states. The analysis of spectra and fitting the frequencies in these states give rotational parameters with higher accuracy compare with previous works. The parameter HJ= -0.107(96) mHz was determined for CH3C15N for the first time.

The lengthening of the HF bond on formation of heterodimers B • • • HF: determination and dependence on the strength of the hydrogen bond

1986 ◽  
Vol 404 (1826) ◽  
pp. 89-99 ◽  
Keyword(s):  
Hydrogen Bond ◽  
Nuclear Spin ◽  
Hyperfine Coupling ◽  
Coupling Constants ◽  
Rotational Spectra ◽  
Bond Stretching ◽  
Monotonically Increasing Function ◽  
First Time ◽  
Increasing Function

We report a procedure that for the first time allows the quantitative determination of the lengthening δr of the HF bond on formation of an isolated hydrogen-bonded dimer B···HF. We show how δr can be obtained from the ground-state hyperfine coupling constants X (D nuclear quadrupole) and D HF (H, F nuclear spin to nuclear spin), which are available from the rotational spectra of the molecules B···H(D)F. We establish the values of δr for the series of heterodimers B···HF where B = Ar, Kr, Xe, N 2 , CO, H 2 S, HCN, CH 3 CN and H 2 O. The values of δr are zero for the first three members of this series and then 0.001, 0.007, 0.010, 0.014, 0.016 and 0.015 Å, respectively (1 Å = 10 -1 nm = 10 -10 m). It is found that δr is a monotonically increasing function of the hydrogen-bond stretching force constant k σ , which is taken as a convenient measure of the hydrogen bond strength.

scholarly journals KiDS+VIKING-450: Cosmic shear tomography with optical and infrared data

2020 ◽  
Vol 633 ◽  
pp. A69 ◽  
Author(s):  
H. Hildebrandt ◽  
F. Köhlinger ◽  
J. L. van den Busch ◽  
B. Joachimi ◽  
C. Heymans ◽  
...  
Keyword(s):  
Near Infrared ◽  
Wide Field ◽  
Photometric Redshifts ◽  
Data Set ◽  
Dark Energy Survey ◽  
Cosmic Shear ◽  
First Time ◽  
Energy Survey ◽  
Infrared Data

We present a tomographic cosmic shear analysis of the Kilo-Degree Survey (KiDS) combined with the VISTA Kilo-Degree Infrared Galaxy Survey. This is the first time that a full optical to near-infrared data set has been used for a wide-field cosmological weak lensing experiment. This unprecedented data, spanning 450 deg2, allows us to significantly improve the estimation of photometric redshifts, such that we are able to include robustly higher-redshift sources for the lensing measurement, and – most importantly – to solidify our knowledge of the redshift distributions of the sources. Based on a flat ΛCDM model we find S8 ≡ σ8 Ωm/0.3 = 0.737+0.040−0.036 in a blind analysis from cosmic shear alone. The tension between KiDS cosmic shear and the Planck-Legacy CMB measurements remains in this systematically more robust analysis, with S8 differing by 2.3σ. This result is insensitive to changes in the priors on nuisance parameters for intrinsic alignment, baryon feedback, and neutrino mass. KiDS shear measurements are calibrated with a new, more realistic set of image simulations and no significant B-modes are detected in the survey, indicating that systematic errors are under control. When calibrating our redshift distributions by assuming the 30-band COSMOS-2015 photometric redshifts are correct (following the Dark Energy Survey and the Hyper Suprime-Cam Survey), we find the tension with Planck is alleviated. The robust determination of source redshift distributions remains one of the most challenging aspects for future cosmic shear surveys.

scholarly journals Methanol formation in TW Hya and future prospects for detecting larger complex molecules in disks with ALMA

2017 ◽  
Vol 13 (S332) ◽  
pp. 395-402 ◽  
Author(s):  
Catherine Walsh ◽  
Shreyas Vissapragada ◽  
Harry McGee
Keyword(s):  
Gas Phase ◽  
Signal To Noise Ratio ◽  
Energy Levels ◽  
Complex Molecules ◽  
Rotational Spectra ◽  
Chemical Models ◽  
Methanol Formation ◽  
Peak Abundance ◽  
Abundance And Distribution ◽  
First Time

AbstractGas-phase methanol was recently detected in a protoplanetary disk for the first time with ALMA. The peak abundance and distribution of methanol observed in TW Hya differed from that predicted by chemical models. Here, the chemistry of methanol gas and ice is calculated using a physical model tailored for TW Hya with the aim to contrast the results with the recent detection in this source. New pathways for the formation of larger complex molecules (e.g., ethylene glycol) are included in an updated chemical model, as well as the fragmentation of methanol ice upon photodesorption. It is found that including fragmentation upon photodesorption improves the agreement between the peak abundance reached in the chemical models with that observed in TW Hya (∼10−11 with respect to H2); however, the model predicts that the peak in emission resides a factor of 2 − 3 farther out in the disk than the ALMA images. Reasons for the persistent differences in the gas-phase methanol distribution between models and the observations of TW Hya are discussed. These include the location of the ice reservoir which may coincide with the compact mm-dust disk (≲ 60 au) and sources of gas-phase methanol which have not yet been considered in models. The possibility of detecting larger molecules with ALMA is also explored. Calculations of the rotational spectra of complex molecules other than methanol using a parametric model constrained by the TW Hya observations suggest that the detection of individual emission lines of complex molecules with ALMA remains challenging. However, the signal-to-noise ratio can be enhanced via stacking of multiple transitions which have similar upper energy levels.

scholarly journals The Microwave Spectrum of Fluoroacetylene in Ground and Vibrationally Excited States and Some Laser Enhancement Effects

1979 ◽  
Vol 34 (3) ◽  
pp. 340-352 ◽  
Author(s):  
Harold Jones ◽  
H. D. Rudolph
Keyword(s):  
Ground State ◽  
Microwave Spectrum ◽  
Vibrational States ◽  
Vibrationally Excited ◽  
Rotational Spectra ◽  
Wave Measurements ◽  
Anharmonicity Constant ◽  
Type V ◽  
First Time

Abstract The microwave spectrum of HCCF and DCCF has been investigated in all vibrational states with energy up to 1500 cm -1 . In the ground state and low-lying vibrational states mm-wave measurements up to 210 GHz were made. In some cases a detailed analysis of the vibrational state rotation spectrum including the effects of l-type resonance, and the determination of the anharmonicity constant gtt was possible. The rotational spectra of combination states of the type (vt = 2, vt′ = 1) were observed and partially analyzed, which is, to our knowledge, the first time this has been accomplished. The low-lying vibrational states of 13 C species of HCCF and DCCF were also observed. The 9.4 μm P(14) CO2-laser line was observed to produce a reduction in intensity in the ground state and an increase in intensity in the v3 = 1 excited state J = 0 → 1, 1 → 2, 2 3 transitions of DCCF.

scholarly journals FIRST DETERMINATION OF THE PROTON’S WEAK CHARGE

2015 ◽  
Vol 8 (1) ◽  
Author(s):  
Shelley A. Page
Keyword(s):  
Standard Model ◽  
High Precision ◽  
Standard Model Prediction ◽  
Data Set ◽  
Weak Charge ◽  
Newport News ◽  
The Standard Model ◽  
First Results ◽  
First Time

The weak charge of the proton has been determined for the first time via a high precision electron-proton scattering experiment, Qweak, carried out at Jefferson Laboratory (JLab) in Newport News, USA. The weak charge is a basic property in subatomic physics, analogous to electric charge. The Standard Model makes a prediction for the weak charges of protons and other particles. First results described here are based on an initial 4% of the data set reported in 20131 , with the ultimate goal of the experiment being a high precision Standard Model test conducted with the full Qweak data set. These initial results are consistent with the Standard Model prediction; they serve as an important first determination of the proton’s weak charge and a proof of principle that the ultimate goals are within reach.

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