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 ALMA-PILS Survey: Formaldehyde deuteration in warm gas on small scales toward IRAS 16293–2422 B

2018 ◽  
Vol 610 ◽  
pp. A54 ◽  
Author(s):  
M. V. Persson ◽  
J. K. Jørgensen ◽  
H. S. P. Müller ◽  
A. Coutens ◽  
E. F. van Dishoeck ◽  
...  
Keyword(s):  
Energy Levels ◽  
Excitation Temperature ◽  
Thermodynamical Equilibrium ◽  
Complex Molecules ◽  
Important Species ◽  
Chemical Models ◽  
Small Scales ◽  
Core Phase ◽  
Low Mass ◽  
First Time

Context.The enhanced degrees of deuterium fractionation observed in envelopes around protostars demonstrate the importance of chemistry at low temperatures, relevant in pre- and protostellar cores. Formaldehyde is an important species in the formation of methanol and more complex molecules.Aims.Here, we aim to present the first study of formaldehyde deuteration on small scales around the prototypical low-mass protostar IRAS 16293–2422 using high spatial and spectral resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations. We determine the excitation temperature, abundances and fractionation level of several formaldehyde isotopologues, including its deuterated forms.Methods.Excitation temperature and column densities of formaldehyde in the gas close to one of the components of the binary were constrained through modeling of optically thin lines assuming local thermodynamical equilibrium. The abundance ratios were compared to results from previous single dish observations, astrochemical models and local ISM values.Results.Numerous isotopologues of formaldehyde are detected, among them H2C17O, and D213CO for the first time in the ISM. The large range of upper energy levels covered by the HDCO lines help constrain the excitation temperature to 106 ± 13 K. Using the derived column densities, formaldehyde shows a deuterium fractionation of HDCO/H2CO = 6.5 ± 1%, D2CO/HDCO = 12.8–4.1+3.3%, and D2CO/H2CO = 0.6(4) ± 0.1%. The isotopic ratios derived are16O/18O = 805–79+43,18O/17O = 3.2–0.3+0.2, and12C/13C = 56–11+8.Conclusions.The HDCO/H2CO ratio is lower than that found in previous studies, highlighting the uncertainties involved in interpreting single dish observations of the inner warm regions. The D2CO/HDCO ratio is only slightly larger than the HDCO/H2CO ratio. This is consistent with formaldehyde forming in the ice as soon as CO has frozen onto the grains, with most of the deuteration happening toward the end of the prestellar core phase. A comparison with available time-dependent chemical models indicates that the source is in the early Class 0 stage.

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.

Application of Novel Low Current OBIRCH Amplifier and Nanoprobing to Identify Subtle Leakages in Advanced Node Technologies

2018 ◽  
Author(s):  
Satish Kodali ◽  
Liangshan Chen ◽  
Yuting Wei ◽  
Tanya Schaeffer ◽  
Chong Khiam Oh
Keyword(s):  
Signal To Noise Ratio ◽  
Semiconductor Industry ◽  
Fault Isolation ◽  
Ring Oscillator ◽  
High Signal ◽  
The Novel ◽  
Resistance Change ◽  
Three Samples ◽  
Relative Threshold ◽  
First Time

Abstract Optical beam induced resistance change (OBIRCH) is a very well-adapted technique for static fault isolation in the semiconductor industry. Novel low current OBIRCH amplifier is used to facilitate safe test condition requirements for advanced nodes. This paper shows the differences between the earlier and novel generation OBIRCH amplifiers. Ring oscillator high standby leakage samples are analyzed using the novel generation amplifier. High signal to noise ratio at applied low bias and current levels on device under test are shown on various samples. Further, a metric to demonstrate the SNR to device performance is also discussed. OBIRCH analysis is performed on all the three samples for nanoprobing of, and physical characterization on, the leakage. The resulting spots were calibrated and classified. It is noted that the calibration metric can be successfully used for the first time to estimate the relative threshold voltage of individual transistors in advanced process nodes.

scholarly journals New Transition and Energy Levels of Three-Times Ionized Krypton (Kr IV)

Atoms ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 48
Author(s):  
M. Raineri ◽  
M. Gallardo ◽  
J. Reyna Almandos ◽  
A. G. Trigueiros ◽  
C. J. B. Pagan
Keyword(s):  
Transition Probabilities ◽  
Energy Levels ◽  
Pulsed Discharge ◽  
Core Polarization ◽  
Polarization Effects ◽  
Hartree Fock ◽  
Theta Pinch ◽  
New Energy ◽  
First Time

A capillary pulsed-discharge and a theta-pinch were used to record Kr spectra in the region of 330–4800 Å. A set of 168 transitions of these spectra were classified for the first time. We extended the analysis to twenty-five new energy levels belonging to 3s23p24d, 3s23p25d even configurations. We calculated weighted transition probabilities (gA) for all of the experimentally observed lines and lifetimes for new energy levels using a relativistic Hartree–Fock method, including core-polarization effects.

scholarly journals Frequency-diverse multimode millimetre-wave constant-ϵr lens-loaded cavity

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
M. A. B. Abbasi ◽  
V. F. Fusco ◽  
O. Yurduseven ◽  
T. Fromenteze
Keyword(s):  
Signal To Noise Ratio ◽  
Cost Effective ◽  
Doa Estimation ◽  
Frequency Diversity ◽  
Millimetre Wave ◽  
Single Lens ◽  
Dielectric Lens ◽  
Diversity Principle ◽  
First Time ◽  
Multi Mode

AbstractThis paper presents a physical frequency-diverse multimode lens-loaded cavity, designed and used for the purpose of the direction of arrival (DoA) estimation in millimetre-wave frequency bands for 5G and beyond. The multi-mode mechanism is realized using an electrically-large cavity, generating spatio-temporally incoherent radiation masks leveraging the frequency-diversity principle. It has been shown for the first time that by placing a spherical constant dielectric lens (constant-ϵr) in front of the radiating aperture of the cavity, the spatial incoherence of the radiation modes can be enhanced. The lens-loaded cavity requires only a single lens and output port, making the hardware development much simpler and cost-effective compared to conventional DoA estimators where multiple antennas and receivers are classically required. Using the lens-loaded architecture, an increase of up to 6 dB is achieved in the peak gain of the synthesized quasi-random sampling bases from the frequency-diverse cavity. Despite the fact that the practical frequency-diverse cavity uses a limited subset of quasi-orthogonal modes below the upper bound limit of the number of theoretical modes, it is shown that the proposed lens-loaded cavity is capable of accurate DoA estimation. This is achieved thanks to the sufficient orthogonality of the leveraged modes and to the presence of the spherical constant-ϵr lens which increases the signal-to-noise ratio (SNR) of the received signal. Experimental results are shown to verify the proposed approach.

CsOH and its Lighter Homologues – a Comparison

2014 ◽  
Vol 69 (11-12) ◽  
pp. 1229-1236
Author(s):  
Matthias Wörsching ◽  
Constantin Hoch
Keyword(s):  
Gas Phase ◽  
Room Temperature ◽  
Structure Type ◽  
Alkali Metal Hydroxide ◽  
X Ray ◽  
Raman Spectroscopic ◽  
Cesium Hydroxide ◽  
Free Ion ◽  
The One ◽  
First Time

Abstract Cesium hydroxide, CsOH, was for the first time characterised on the basis of single-crystal data. The structure is isotypic to the one of the room-temperature modification of NaOH and can be derived from the NaCl structure type thus allowing the comparison of all alkali metal hydroxide structures. Raman spectroscopic investigations show the hydroxide anion to behave almost as a free ion as in the gas phase. The X-ray investigations indicate possible H atom positions.

scholarly journals Extended analysis of Xe VII and Xe VIII

2017 ◽  
Vol 95 (9) ◽  
pp. 805-810 ◽  
Author(s):  
M. Raineri ◽  
M. Gallardo ◽  
J. Reyna Almandos ◽  
C.J.B. Pagan ◽  
R. Sarmiento
Keyword(s):  
Light Source ◽  
Energy Levels ◽  
Excited Configuration ◽  
Pulsed Discharge ◽  
Hartree Fock ◽  
The Core ◽  
New Energy ◽  
Extended Analysis ◽  
First Time ◽  
Atomic Parameters

A pulsed discharge light source to study the six and seven times ionized xenon spectra in the 419–4642 Å region was used. A set of 40 transitions of Xe VII and 25 transitions of Xe VIII were classified for the first time. We revised the values for the previously known energy levels and extended the analysis for Xe VII to 10 new energy levels belonging to 5s6d, 5s7s and 5s7p, 4d95s25p even and odd configurations, respectively. Seven new energy levels of the core excited configuration 4d95s5d of Xe VIII are presented. For the prediction of the atomic parameters, energy levels, and transition, relativistic Hartree–Fock calculations were used.

Analysis of chlorinated hydrocarbons in gas phase using a portable membrane inlet mass spectrometer

2016 ◽  
Vol 8 (36) ◽  
pp. 6607-6615 ◽  
Author(s):  
Stamatios Giannoukos ◽  
Boris Brkić ◽  
Stephen Taylor
Keyword(s):  
Gas Phase ◽  
Mass Spectrometer ◽  
Gaseous Phase ◽  
Chlorinated Hydrocarbons ◽  
Volatile Chlorinated Hydrocarbons ◽  
First Time

A compact portable membrane inlet mass spectrometer (MIMS) has been used for the first time to detect and monitor, both qualitatively and quantitatively, volatile chlorinated hydrocarbons in the gaseous phase.

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