Vibrationally excited states of NC4P: millimetre-wave spectroscopy and coupled cluster calculationsElectronic supplementary information (ESI) available: Experimental frequencies and least-squares residuals (in MHz) for seven vibrational states of NC4P. See http://www.rsc.org/suppdata/cp/b3/b311745f/

2004 ◽  
Vol 6 (1) ◽  
pp. 46 ◽  
Author(s):  
L. Bizzocchi ◽  
C. Degli Esposti ◽  
P. Botschwina
Keyword(s):  
Least Squares ◽  
Excited States ◽  
Supplementary Information ◽  
Coupled Cluster ◽  
Vibrational States ◽  
Vibrationally Excited ◽  
Millimetre Wave

THE HYDROGEN–CHLORINE SYSTEM IN THE MM PRESSURE RANGE: I. ENERGY DISTRIBUTION AMONG VIBRATIONALLY EXCITED STATES

1964 ◽  
Vol 42 (10) ◽  
pp. 2176-2192 ◽  
Author(s):  
F. D. Findlay ◽  
J. C. Polanyi
Keyword(s):  
Excited States ◽  
Rotational Temperature ◽  
Relative Rate ◽  
Infrared Emission ◽  
Vibrational States ◽  
Vibrationally Excited ◽  
Experimental Conditions ◽  
Reduced Pressure ◽  
A Chain ◽  
First Time

When atomic plus molecular hydrogen coming from a Wood's discharge tube are mixed with molecular chlorine, infrared emission is observed (1). At low reagent pressures, ~10−2 mm Hg, this emission can be related to the relative rate of the reaction H + Cl2 → HCl†ν + Cl proceeding to form HCl in vibrationally excited states ν = 1–6, of the ground electronic state. In the present work this system has been investigated for the first time at ~100 × the reagent pressure (~1 mm Hg). The reaction was shown to proceed by a chain mechanism. The translational–rotational temperature was 1300 ± 100 °K under the experimental conditions normally used. The vibrational distribution was notable for the presence of vibrators in levels ν = 7 and 8, which are respectively 4 and 10 kcal higher in energy than the exothermicity of the H + Cl2 reaction. The population in these levels appeared to be related to that in the levels with [Formula: see text]; it was proposed that vibrational–vibrational exchange among these lower levels was responsible for populating the higher ones. A simple model yielded a collision efficiency for HCl†ν=1 + HCl†ν=6 → HCl†ν=7 + HCl†ν=0, of Z1,6t = 6 × 103 collisions per transfer. Addition of HCl to the reaction mixture brought about a redistribution among vibrationally excited states indicative of a fast vibrational transfer, HClν=0 + HCl†ν=2 → 2 HCl†ν=1.At reduced pressure of HCl† the stationary-state distribution among higher vibrational states approximated closely to that observed at 10−2 mm Hg total pressure (where collisional deactivation is insignificant), suggesting that collisional deactivation was not of major importance even at the pressure used in the present work. In order to account for the high translational–rotational temperature, in the absence of substantial vibrational deactivation, it was necessary to suppose that the greater part of the energy liberated by the reaction H + Cl2 went directly into translational and rotational motion of the products.

scholarly journals Chirped-pulse Fourier transform millimeter-wave spectroscopy of ten vibrationally excited states of i-propyl cyanide: exploring the far-infrared region

2017 ◽  
Vol 19 (3) ◽  
pp. 1751-1756 ◽  
Author(s):  
Benjamin E. Arenas ◽  
Sébastien Gruet ◽  
Amanda L. Steber ◽  
Barbara M. Giuliano ◽  
Melanie Schnell
Keyword(s):  
Excited States ◽  
Far Infrared ◽  
Infrared Region ◽  
Interstellar Space ◽  
Frequency Range ◽  
Vibrationally Excited ◽  
Data Set ◽  
Millimetre Wave ◽  
Chirped Pulse ◽  
Millimeter Wave Spectroscopy

The astrochemically relevant molecule i-propyl cyanide is studied in the millimetre wave frequency range. The extensive data set for isotopologues and ten vibrationally excited states will support further astronomical searches and identifications, such as in warmer regions of interstellar space.

Microwave Spectrum of Chloroacetylene in Ground and Excited Vibrational States

1978 ◽  
Vol 33 (2) ◽  
pp. 156-163 ◽  
Author(s):  
Harold Jones ◽  
Michio Takami ◽  
John Sheridan
Keyword(s):  
Excited States ◽  
Microwave Spectrum ◽  
Coupling Constants ◽  
Spectroscopic Constants ◽  
Frequency Range ◽  
Vibrational States ◽  
Vibrationally Excited ◽  
Rotational Spectra ◽  
Isotopic Species ◽  
Quadrupole Coupling

The microwave spectrum of chloroacetylene in the ground and excited states has been investigated in the frequency range 15 to 306 GHz. Ground state rotational and nuclear quadrupole coupling constants for twelve isotopic species of chloroacetylene and accurate distortion constants were determined for two of these. The data allowed the rs-structure of chloroacetylene to be reconsidered and the internal consistency of this method of structure determination to be checked. Rotational spectra in five vibrationally excited states, with energy up to 700 cm-1 were observed for four different isotopic species and spectroscopic constants for these states were derived.

Vibrationally excited states of HC5N: millimeter-wave spectroscopy and coupled cluster calculations

2005 ◽  
Vol 230 (2) ◽  
pp. 185-195 ◽  
Author(s):  
C. Degli Esposti ◽  
L. Bizzocchi ◽  
P. Botschwina ◽  
K.M.T. Yamada ◽  
G. Winnewisser ◽  
...  
Keyword(s):  
Excited States ◽  
Millimeter Wave ◽  
Coupled Cluster ◽  
Vibrationally Excited ◽  
Millimeter Wave Spectroscopy ◽  
Cluster Calculations ◽  
Coupled Cluster Calculations

scholarly journals Far-infrared laboratory spectroscopy of aminoacetonitrile and first interstellar detection of its vibrationally excited transitions

2020 ◽  
Vol 641 ◽  
pp. A160 ◽  
Author(s):  
M. Melosso ◽  
A. Belloche ◽  
M.-A. Martin-Drumel ◽  
O. Pirali ◽  
F. Tamassia ◽  
...  
Keyword(s):  
Spectral Line ◽  
Excited States ◽  
Ground State ◽  
Far Infrared ◽  
Continuum Emission ◽  
Vibrational States ◽  
Vibrationally Excited ◽  
Synchrotron Source ◽  
Star Forming ◽  
Vibration Rotation

Context. Aminoacetonitrile, a molecule detected in the interstellar medium only toward the star-forming region Sagittarius B2 (Sgr B2), is considered an important prebiotic species; in particular, it is a possible precursor of the simplest amino acid glycine. To date, observations have been limited to ground state emission lines, whereas transitions from within vibrationally excited states remained undetected. Aims. We wanted to accurately determine the energies of the low-lying vibrational states of aminoacetonitrile, which are expected to be populated in Sgr B2(N1), the main hot core of Sgr B2(N). This step is fundamental in order to properly evaluate the vibration-rotation partition function of aminoacetonitrile as well as the line strengths of the rotational transitions of its vibrationally excited states. This is necessary to derive accurate column densities and secure the identification of these transitions in astronomical spectra. Methods. The far-infrared ro-vibrational spectrum of aminoacetonitrile has been recorded in absorption against a synchrotron source of continuum emission. Three bands, corresponding to the lowest vibrational modes of aminoacetonitrile, were observed in the frequency region below 500 cm−1. The combined analysis of ro-vibrational and pure rotational data allowed us to prepare new spectral line catalogs for all the states under investigation. We used the imaging spectral line survey ReMoCA performed with ALMA to search for vibrationally excited aminoacetonitrile toward Sgr B2(N1). The astronomical spectra were analyzed under the local thermodynamic equilibrium (LTE) approximation. Results. Almost 11 000 lines have been assigned during the analysis of the laboratory spectrum of aminoacetonitrile, thanks to which the vibrational energies of the v11 = 1, v18 = 1, and v17 = 1 states have been determined. The whole dataset, which includes high J and Ka transitions, is well reproduced within the experimental accuracy. Reliable spectral predictions of pure rotational lines can now be produced up to the THz region. On the basis of these spectroscopic predictions, we report the interstellar detection of aminoacetonitrile in its v11 = 1 and v18 = 1 vibrational states toward Sgr B2(N1) in addition to emission from its vibrational ground state. The intensities of the identified v11 = 1 and v18 = 1 lines are consistent with the detected v = 0 lines under LTE at a temperature of 200 K for an aminoacetonitrile column density of 1.1 × 1017 cm−2. Conclusions. This work shows the strong interplay between laboratory spectroscopy exploiting (sub)millimeter and synchrotron-based far-infrared techniques, and observational spectral surveys to detect complex organic molecules in space and quantify their abundances.

scholarly journals Detection of vibrationally excited HC7N and HC9N in IRC +10216

2020 ◽  
Vol 640 ◽  
pp. L13 ◽  
Author(s):  
J. R. Pardo ◽  
C. Bermúdez ◽  
C. Cabezas ◽  
M. Agúndez ◽  
J. D. Gallego ◽  
...  
Keyword(s):  
Excited States ◽  
Density Ratio ◽  
Rotational Constant ◽  
Complete Characterization ◽  
Vibrational States ◽  
Vibrationally Excited ◽  
Carbon Chains ◽  
Quantum Numbers ◽  
Integer Quantum ◽  
Bending Modes

Observations of IRC +10216 with the Yebes 40 m telescope between 31 and 50 GHz have revealed more than 150 unidentified lines. Some of them can be grouped into a new series of 26 doublets, harmonically related with integer quantum numbers ranging from Jup = 54 to 80. The separation of the doublets increases systematically with J, that is to say, as expected for a linear species in one of its bending modes. The rotational parameters resulting from the fit to these data are B = 290.8844 ± 0.0004 MHz, D = 0.88 ± 0.04 Hz, and q = 0.1463 ± 0.0001 MHz. The rotational constant is very close to that of the ground state of HC9N. Our ab initio calculations show an excellent agreement between these parameters and those predicted for the lowest energy vibrationally excited state, ν19 = 1, of HC9N. This is the first detection, and complete characterization in space, of vibrationally excited HC9N. An energy of 41.5 cm−1 is estimated for the ν19 state. In addition, 17 doublets of HC7N in the ν15 = 1 state, for which laboratory spectroscopy is available, were detected for the first time in IRC +10216. Several doublets of HC5N in its ν11 = 1 state were also observed. The column density ratio between the ground and the lowest excited vibrational states are ≈127, 9.5, and 1.5 for HC5N, HC7N, and HC9N, respectively. We find that these lowest-lying vibrational states are most probably populated via infrared pumping to vibrationally excited states lying at ≈600 cm−1. The lowest vibrationally excited states thus need to be taken into account to precisely determine absolute abundances and abundance ratios for long carbon chains. The abundance ratios N(HC5N)/N(HC7N) and N(HC7N)/N(HC9N) are 2.4 and 7.7, respectively.

scholarly journals The Populations of H2 Vibrational States in Intense UV Fields Near O-B Stars

1987 ◽  
Vol 115 ◽  
pp. 179-180
Author(s):  
P. E. Dewdney ◽  
R. S. Roger ◽  
N. Robert
Keyword(s):  
Electronic State ◽  
Excited States ◽  
Ground State ◽  
Molecular Hydrogen ◽  
Ground Electronic State ◽  
Vibrational States ◽  
Vibrationally Excited ◽  
B Stars ◽  
Intense Fields ◽  
The Mean

In most places where molecular hydrogen exists in the interstellar medium, it will be found in the ground vibrational and ground electronic state. This will not be so, however, near 0 or early B stars where, in the region just beyond the ionization boundary, populations will be determined by UV fields up to 105 times more intense than the mean interstellar value (4 × 10−16 ergs cm−3 s−1 = 1 Habing unit). The H2 absorbs Lyman-Werner band photons longwards of λ91 nm and subsequent decays to the ground electronic state may lead to dissociation (vibrational continuum) or to one of 14 vibrationally excited states. Molecules in these states have lifetimes of order 1010 s and, in the intense fields, will be exposed to further Lyman-Werner excitation. The probability of dissociation is therefore greatly enhanced by this ‘multiple excitation’, since the number of lines available to vibrationally excited H2 is many times that available to ground-state H2 (Shull, 1978).

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