PREDISSOCIATIONS OF THE C12O AND C13O MOLECULES

1955 ◽  
Vol 33 (3-4) ◽  
pp. 125-132 ◽  
Author(s):  
A. E. Douglas ◽  
C. K. Møller
Keyword(s):  
Ground State ◽  
Good Evidence ◽  
High Dispersion ◽  
Dissociation Limit ◽  
Π State

The Ångström bands of C12O and C13O have been photographed with a high dispersion spectrograph and the predissociations previously reported in these bands have been re-examined. The predissociations provide good evidence that C12O has a dissociation limit 89595 ± 30 cm.−1 above the ν = 0 level of the ground state. The fourth positive (A1Π − X1Σ) bands have been re-examined and it has been shown that, contrary to earlier reports, there is no evidence for predissociation in the A1Π state.

ULTRAVIOLET SPECTRA OF LiH AND LiD

1957 ◽  
Vol 35 (10) ◽  
pp. 1204-1214 ◽  
Author(s):  
R. Velasco
Keyword(s):  
Excited State ◽  
Ground State ◽  
Band System ◽  
Electronic States ◽  
High Dispersion ◽  
Dissociation Energies ◽  
Near Ultraviolet ◽  
Path Lengths ◽  
Vibrational Constants ◽  
Π State

The absorption spectra of LiH and LiD have been observed in the near ultraviolet with high dispersion and absorbing path lengths up to 16 meters. A new band system has been found in each molecule involving the ground state and a 1Π excited state. Rotational and vibrational analyses of this system have been carried out and rotational and vibrational constants for the upper state have been determined. The observed breaking off of the rotational structure of the bands of this B1Π—X1Σ+ system has been interpreted as due to predissociation by rotation. With this assumption very accurate dissociation limits of the B1Π state have been obtained. From these dissociation limits the dissociation energies of the three known electronic states of LiH and LiD have been calculated. In particular the dissociation energies (D0) of the ground states of LiH and LiD have been found to be 2.4288 ± 0.0002 ev. and 2.4509 ± 0.0010 ev., respectively.

New emission band systems of the NH+ molecule

1968 ◽  
Vol 46 (1) ◽  
pp. 61-73 ◽  
Author(s):  
R. Colin ◽  
A. E. Douglas
Keyword(s):  
Radio Astronomy ◽  
Ground State ◽  
Emission Band ◽  
Single Band ◽  
Absorption Lines ◽  
High Dispersion ◽  
Rotational Constants ◽  
Interstellar Absorption ◽  
Isotopic Species ◽  
Π State

Two new band systems of the NH+ molecule have been photographed at high dispersion and analyzed. One system consists of a single band at 4348.5 Å which arises from a 2Δ–2Π transition and the second consists of three bands of a 2Σ−–2Π transition with the strongest (0–0) band lying at 4628.9 Å. A number of the vibrational and rotational constants of these states have been determined. From a study of the isotopic species 14NH+, 15NH+, and 14ND, it has been established that the ground state of NH+ is the 2Π state and that a 4Σ− state lies 354 cm−1 higher. The spectrum has allowed us to determine the wavelengths at which cometary spectra and interstellar absorption lines of NH+ are expected to fall and to predict that the transition between the two lowest levels, which may be of interest to radio astronomy, occurs at 13 500 mc/s.

Excited-State Dynamics in the RNA Nucleotide Uridine 5’-Monophosphate Investigated by Femtosecond Broadband Transient Absorption Spectroscopy

2019 ◽  
Author(s):  
Matthew M. Brister ◽  
Carlos Crespo-Hernández
Keyword(s):  
Excited State ◽  
Excited States ◽  
Ground State ◽  
Transient Absorption ◽  
Electronic Energy ◽  
Transient Absorption Spectroscopy ◽  
Electronic Relaxation ◽  
Vibrationally Excited ◽  
Excited State Dynamics ◽  
Π State

<p></p><p> Damage to RNA from ultraviolet radiation induce chemical modifications to the nucleobases. Unraveling the excited states involved in these reactions is essential, but investigations aimed at understanding the electronic-energy relaxation pathways of the RNA nucleotide uridine 5’-monophosphate (UMP) have not received enough attention. In this Letter, the excited-state dynamics of UMP is investigated in aqueous solution. Excitation at 267 nm results in a trifurcation event that leads to the simultaneous population of the vibrationally-excited ground state, a longlived <sup>1</sup>n<sub>O</sub>π* state, and a receiver triplet state within 200 fs. The receiver state internally convert to the long-lived <sup>3</sup>ππ* state in an ultrafast time scale. The results elucidate the electronic relaxation pathways and clarify earlier transient absorption experiments performed for uracil derivatives in solution. This mechanistic information is important because long-lived nπ* and ππ* excited states of both singlet and triplet multiplicities are thought to lead to the formation of harmful photoproducts.</p><p></p>

ROTATIONAL ANALYSIS OF THE β BANDS OF PHOSPHORUS MONOXIDE

1959 ◽  
Vol 37 (2) ◽  
pp. 136-143 ◽  
Author(s):  
Nand Lal Singh
Keyword(s):  
Ground State ◽  
Band System ◽  
Electronic States ◽  
Rotational Analysis ◽  
Rotational Constants ◽  
Fine Structures ◽  
Π State

The fine structures of three of the β bands of PO which occur near 3200 Å have been analyzed. The analysis shows that the upper state of this band system is a 2Σ and not a 2Π state as previously believed. The rotational constants of both electronic states have been determined and it is found that the ground state constants, previously determined from the γ bands, are incorrect.

THE ABSORPTION SPECTRUM OF CF2

1967 ◽  
Vol 45 (7) ◽  
pp. 2355-2374 ◽  
Author(s):  
C. Weldon Mathews
Keyword(s):  
Absorption Spectrum ◽  
Electronic State ◽  
Ground State ◽  
Band System ◽  
Electronic States ◽  
Vibrational Structure ◽  
Rotational Structure ◽  
Transition Moment ◽  
High Dispersion ◽  
Parallel Type

The absorption spectrum of CF2 in the 2 500 Å region has been photographed at high dispersion, and the rotational structure of a number of bands has been analyzed. The analysis of the well-resolved subbands establishes that these are perpendicular- rather than parallel-type bands, as previously assigned. Further analysis shows that the upper and lower electronic states are of 1B1 and 1A1symmetries respectively, corresponding to a transition moment that is perpendicular to the plane of the molecule. In the upper electronic state, r0(CF) = 1.32 Å and [Formula: see text], while in the ground state, r0(CF) = 1.300 Å and [Formula: see text]. An investigation of the vibrational structure of the band system has shown that the vibrational numbering in ν2′ must be increased by one unit from earlier assignments, thus placing the 000–000 band near 2 687 Å (37 220 cm−1). A search between 1 300 and 8 500 Å showed two new band systems near 1 350 and 1 500 Å which have been assigned tentatively to the CF2 molecule.

Rotational Analysis of the lΠ–XlΣ+ System of C80Se

1974 ◽  
Vol 52 (9) ◽  
pp. 813-820 ◽  
Author(s):  
René Stringat ◽  
Jean-Paul Bacci ◽  
Marie-Hélène Pischedda
Keyword(s):  
Emission Spectrum ◽  
Ground State ◽  
High Frequency ◽  
Rotational Analysis ◽  
Molecular Constants ◽  
High Frequency Discharge ◽  
Perturbed State ◽  
Simple Evaluation ◽  
Π State

The strongly perturbed 1Π–X1Σ+ system of C80Se has been observed in the emission spectrum of a high frequency discharge through selenium and carbon traces in a neon atmosphere. The analysis of five bands yields, for the molecular constants of the ground state, the values Be″ = 0.5750 cm−1, [Formula: see text], αe″ = 0.00379 cm−1, re″ = 1.676 Å, ΔG″(1/2) = 1025.64 cm−1, and ΔG″(3/2) = 1015.92 cm−1. The numerous perturbations in the 1Π state prohibit the simple evaluation of the constants of the perturbed state and of the perturbing ones.

THE LYMAN BANDS OF MOLECULAR HYDROGEN

1959 ◽  
Vol 37 (5) ◽  
pp. 636-659 ◽  
Author(s):  
G. Herzberg ◽  
L. L. Howe
Keyword(s):  
High Resolution ◽  
Vibrational Level ◽  
Ground State ◽  
Molecular Hydrogen ◽  
Equilibrium Constants ◽  
Dissociation Limit ◽  
Vibrational Levels ◽  
State Formula ◽  
Single Formula ◽  
Vibrational Constants

The Lyman bands of H2 have been investigated under high resolution with a view to improving the rotational and vibrational constants of H2 in its ground state. Precise Bv and ΔG values have been obtained for all vibrational levels of the ground state. One or two of the highest rotational levels of the last vibrational level (v = 14) lie above the dissociation limit. Both the [Formula: see text] and ΔG″ curves have a point of inflection at about v″ = 3. This makes it difficult to represent the whole course of each of these curves by a single formula and therefore makes the resulting equilibrium constants somewhat uncertain. This uncertainty is not very great for the rotational constants for which we find[Formula: see text]but is considerable for the vibrational constants ωe and ωexe for which three-, four-, five-, and six-term formulae give results diverging by ± 1 cm−1. The rotational and vibrational constants for the upper state [Formula: see text] of the Lyman bands are also determined. An appreciable correction to the position of the upper state is found.

THE b1Σ+–X3Σ− BAND SYSTEM OF NF

1966 ◽  
Vol 44 (10) ◽  
pp. 2251-2258 ◽  
Author(s):  
A. E. Douglas ◽  
W. E. Jones
Keyword(s):  
Ground State ◽  
Band System ◽  
High Dispersion ◽  
Rotational Analysis ◽  
Strong Band

If argon mixed with a small amount of NF3 is pumped rapidly through a mild discharge, a green glow is observed downstream from the discharge. This emission has been photographed with a high dispersion spectrograph and found to consist of a strong band with a head at 5 288 Å and a number of weaker bands. A rotational analysis of the bands has shown that they are the b1Σ+–X3Σ− bands of the NF molecule. The constants of the two states have been determined and it is found that for the ground state, ωe = 1 141.37 cm−1 and re = 1.317 3 Å.

Laser-rf double-resonance study of SiO+

1995 ◽  
Vol 73 (1-2) ◽  
pp. 101-105 ◽  
Author(s):  
T. J. Scholl ◽  
R. Cameron ◽  
S. D. Rosner ◽  
R. A. Holt
Keyword(s):  
Fine Structure ◽  
Ground State ◽  
Molecular Model ◽  
Double Resonance ◽  
Rotational Quantum Number ◽  
Resonance Method ◽  
Rotational Transition ◽  
Quantum Numbers ◽  
Data Yield ◽  
Π State

We used the laser-rf double resonance method to measure 15 fine structure intervals for rotational quantum numbers ranging from N = 5 to 79 of the ν = 0 level of the X2Σ+ state of SiO+. We present a molecular model, including perturbations from the A2Π state, which explains the observed strong variation of fine structure as a function of rotational quantum number. These data yield greatly improved predictions of the microwave spectrum of the ground state of SiO+. In particular we predicted the ground state rotational transition (N = 2, J = 5/2) → (N = 1, J = 3/2) to be 86 063(1) MHz, confirming that this transition is not the source of the radio line known as U86.2 at 86 243.45(40) MHz.

Dissociative Electron Attachment Processes in SO2 and NO2

1971 ◽  
Vol 49 (9) ◽  
pp. 1571-1574 ◽  
Author(s):  
D. A. Rallis ◽  
J. M. Goodings
Keyword(s):  
Kinetic Energy ◽  
Ground State ◽  
Electronic Excitation ◽  
Electron Attachment ◽  
Negative Ion ◽  
Dissociation Limit ◽  
Dissociative Electron Attachment ◽  
Zero Kinetic Energy ◽  
Trapped Electron ◽  
Second Peak

A trapped electron apparatus has been used to identify the processes involved in negative ion formation for the triatomic oxides SO2 and NO2. Two O− peaks are observed in SO2 with onset values at 4.2 ± 0.15 and 6.3 ± 0.2 eV, and peak values at 5.0 ± 0.15 and 7.4 ± 0.15 eV, respectively. From kinetic energy analysis of the O− ions, both peaks are found to have the same dissociation limit involving SO in its ground state. For NO2, two dissociative electron attachment peaks are observed with onset values at 1.6 ± 0.2 and 7.3 ± 0.3 eV, and peak values at 3.0 ± 0.2 and 8.1 ± 0.2 eV, respectively. The first broad peak is explained by overlapping contributions from two processes having the same dissociation limit involving ground state NO; they differ only in the amount of kinetic energy possessed by the fragments. The second peak appears to involve electronic excitation of the neutral fragment NO* with zero kinetic energy at onset.

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