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.

Potential-energy curves, zero-field splittings, and radiative lifetimes for low-lying states of AsH

1987 ◽  
Vol 65 (2) ◽  
pp. 155-164 ◽  
Author(s):  
Toshio Matsushita ◽  
Christel M. Marian ◽  
Rainer Klotz ◽  
Sigrid D. Peyerimhoff
Keyword(s):  
Fine Structure ◽  
Potential Energy ◽  
Ground State ◽  
Zero Order ◽  
Potential Energy Curves ◽  
Basis Set ◽  
Zero Field ◽  
Spin Orbit ◽  
Spin Orbit Interactions ◽  
Π State

Large-scale multireference configuration-interaction (MRD-CI) calculations in an atomic-orbital (AO) basis set containing up to f functions on As and d on hydrogen are employed to study the potential-energy curves of the π2(X3Σ−, a1Δ, b1Σ+), the σ → π, and the π → σ3.1Π states; a large number of σ → σ* states; and the lowest π → s,p Rydberg series. The σ → σ* states are strongly repulsive and exhibit numerous interactions with the Rydberg members causing predissociation. The probabilities for the spin-forbidden transitions from b1Σ+and a1Δ to the X3Σ−ground state as well as the zero-field splittings of theX3Σ−and A3Π states have been evaluated by employing a variational perturbation scheme in which the zero-order wave functions are MRD-CI expansions. The perturber states are determined by their spin-orbit interactions, which are calculated by employing the Breit–Pauli one- and two-electron spin-orbit operator. The radiative lifetime of the b1Σ+ state is predicted to be 0.35 ms, whereby the dominant mechanism is deactivation to the ms = ±1 component.The parallel transition is found to be much weaker. The lifetime of a1Δ is calculated to be 22 ms, whereby the process [Formula: see text] is favored. Both b–X and a–X transitions borrow their intensity primarily from the A3Π–X3Σ− transition and, furthermore, the 1Π–a1Δ and higher 3,1Π state spin-allowed transitions. The probability for the quadrupole b–a transition is evaluated to be three orders of magnitude smaller than the b–X transition. The calculated zero-field splitting of the X3Σ− ground state amounts to 101.4 cm−1, and the fine-structure splitting between the 2, 1, and 0+ components of the A3Π state evaluated to be 544.5 and 674.4 cm−1, respectively, in good accord with experimental results; whereas the calculated Λ doubling of the0+–0− fine-structure levels of the A3Π state (35.2 cm−1 vs. 44.72 cm−1) is too small in the present treatment. The dependence of spin-orbit effects and transition probabilities on AO basis sets and relativistic corrections to the zero-order Hamiltonian are discussed, and it is concluded that lifetime calculations for spin-forbidden processes in first- and second-row molecules can be extended in a fairly straightforward manner to systems with considerable spin-orbit interactions.

scholarly journals The Submillimeter Wave Astronomy Satellite

1990 ◽  
Vol 123 ◽  
pp. 251-251 ◽  
Author(s):  
G.J. Melnick
Keyword(s):  
Fine Structure ◽  
Chemical Composition ◽  
Ground State ◽  
Molecular Clouds ◽  
Large Scale ◽  
Rotational Transition ◽  
Submillimeter Wave ◽  
Important Species ◽  
Structure Transition ◽  
Large Scale Survey

AbstractThe Submillimeter Wave Astronomy Satellite (SWAS) is a NASA Small-Explorer Class experiment whose objective is to study both the chemical composition and the thermal balance in dense (NH2 > 103 cm−3) molecular clouds and, by observing many clouds throughout our galaxy, relate these conditions to the processes of star formation. To conduct this study SWAS will be capable of carrying out both pointed and scanning observations simultaneously in the lines of four important species: (1) the H2O (110–101) 556.963 GHz ground-state ortho transition, (2) the O2 (3,3–1,2) 487.249 GHz transition, (3) the CI (3P1 – 3P0) 492.162 GHz ground-state fine structure transition, and (4) the 13CO (J = 5–4) 550.926 GHz rotational transition. These atoms and molecules are predicted to be among the most abundant within molecular clouds and, because they possess low-lying transitions with energy differences (ΔE/k) between 15 and 30K (temperatures typical of many molecular clouds), these species are believed to be dominant coolants of the gas as it collapses to form stars and planets. A large-scale survey in these lines is virtually impossible from any platform within the atmosphere due to telluric absorption.

Double resonance rotational spectroscopy of He–HCO+

2019 ◽  
Vol 21 (7) ◽  
pp. 3440-3445 ◽  
Author(s):  
Thomas Salomon ◽  
Matthias Töpfer ◽  
Philipp Schreier ◽  
Stephan Schlemmer ◽  
Hiroshi Kohguchi ◽  
...  
Keyword(s):  
Ground State ◽  
Double Resonance ◽  
Rotational Transition ◽  
Rotational Spectroscopy ◽  
Vibrational Transition ◽  
Resonance Technique ◽  
Dissociative State

The ground state of He–HCO+ is investigated using a recently developed double resonance technique, consisting of a rotational transition followed by a vibrational transition into a dissociative state.

scholarly journals Infrared emission lines from celestial sources

1965 ◽  
Vol 23 ◽  
pp. 299-302
Author(s):  
Robert J. Gould
Keyword(s):  
Fine Structure ◽  
Ground State ◽  
Hydrogen Molecule ◽  
Infrared Region ◽  
Infrared Emission ◽  
Rotational Transition ◽  
Emission Lines ◽  
H Ii Regions ◽  
Para Hydrogen ◽  
Stellar Envelopes

Some possible strong astronomical emission lines in the infrared region are discussed. The line at 12.8 microns, which results from a transition between the fine structure components of the ground state of the ion Ne+, is thought to be emitted from galactic H II regions and also possibly from extended stellar envelopes. The line at 28 microns is emitted in the J = 2 to J = 0 rotational transition in the (para) hydrogen molecule, and could be emitted from interstellar H I regions and from collapsing protostars. Estimates of the expected intensities of these astronomical emission lines are given.

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.

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