Microwave Spectra of Furazan. IV. Rotation Spectra of Vibrationally Excited States of Perdeuterated Furazan

Abstract The pure rotation spectra of molecules in 25 vibrationally excited states of perdeuterated furazan, C2D2N2O, have been studied by double resonance modulation (DRM) microwave spectroscopy. Twelve of these spectra have been correlated, -on the basis of relative intensity measurements under DRM -, with fundamental vibrations as previously established by IR spectroscopy. Rotational parameters for these 12 fundamental levels are reported, and the contributions to the effective rotational constants and to the inertia defect of the ground state of d2 -furazan have been determined for 10 modes of vibration.

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High-Resolution Vibrational Spectra of Furazan

Zeitschrift für Naturforschung A ◽

10.1515/zna-1991-1002 ◽

1991 ◽

Vol 46 (10) ◽

pp. 841-850

Author(s):

Otto L. Stiefvater

Keyword(s):

Excited States ◽

Ground State ◽

Double Resonance ◽

Microwave Spectroscopy ◽

Statistical Uncertainty ◽

Molecular Constants ◽

Vibrationally Excited ◽

Vibrational Ground State ◽

Vibrational Bands ◽

Ft Ir

AbstractThe study by Fourier transform (FT) infrared (IR) spectroscopy of the fundamental vibrational bands v12 and v5 of furazan yields the origins of these bands with a statistical uncertainty of 10-6 cm-1, which leads to an estimated absolute uncertainty of 10-4 cm-1. The values are v°12 = 952.6123 cm -1 and v°5 = 1.005.3536 cm -1. They confirm the values previously deduced from laser/microwave double resonance (LMDR) experiments. Previous results for the molecular constants of the vibrational ground state and of the two vibrationally excited states, as obtained by double resonance modulation (DRM) microwave spectroscopy alone, are confirmed and refined. Advantages brought about through the combination of the DRM microwave and the FT-IR technique are outlined.

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Preferred Rotameric Conformations of Isobutyraldehyde, Their Dipole Moments and Vibrationally Excited States by Microwave Spectroscopy

Zeitschrift für Naturforschung A ◽

10.1515/zna-1986-0305 ◽

1986 ◽

Vol 41 (3) ◽

pp. 483-490 ◽

Cited By ~ 1

Author(s):

O. L. Stiefvater

Keyword(s):

Oxygen Atom ◽

Excited States ◽

Ground State ◽

Dipole Moments ◽

Microwave Spectroscopy ◽

Centrifugal Distortion ◽

Gauche Conformation ◽

Vibrationally Excited ◽

Trans Conformation ◽

Centrifugal Distortion Constants

The earlier prediction of the preferred and the less stable rotameric conformations of isobutyraldehyde, (CH3)2CHCHO, has been confirmed experimentally by microwave spectroscopy. The compound exists mainly in a gauche conformation, in which one of the methyl groups is eclipsed by the oxygen atom, and the less stable rotamer is the trans conformation, in which the oxygen atom eclipses the isopropyl hydrogen.Ground state rotational constants (in MHz) and centrifugal distortion constants (in kHz), together with dipole moments (in D), are:Rotation spectra due to three torsionally excited states of each rotamer have been identified, along with satellites arising from CH3 internal rotation and CC2 wagging.

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THE HYDROGEN–CHLORINE SYSTEM IN THE MM PRESSURE RANGE II. THE VIBRATIONAL GROUND STATE STUDIED BY SELF-ABSORPTION

Canadian Journal of Chemistry ◽

10.1139/v64-324 ◽

1964 ◽

Vol 42 (10) ◽

pp. 2193-2200 ◽

Cited By ~ 8

Author(s):

J. R. Alrey ◽

F. D. Findlay ◽

J. C. Polanyi

Keyword(s):

Excited States ◽

Relative Intensity ◽

Ground State ◽

Pressure Range ◽

Infrared Emission ◽

Absolute Amount ◽

Reaction Products ◽

Vibrationally Excited ◽

Vibrational Ground State ◽

Apparent Deviation

Studies of energy distribution among reaction products, through the agency of infrared chemiluminescence, have previously only yielded information concerning the distribution among vibrationally excited states. In the work described here it was shown that self-absorption of the infrared emission could be used as a measure both of the relative and the absolute amount of product present in the vibrational ground state, ν = 0. Two independent methods were used to measure the extent of self-absorption. The first method relied on measurements of an apparent deviation from Boltzmann-type rotational intensity distribution within the ν(1–0) and ν(2–1) bands. The second method depended on measurements of an apparent deviation of the relative intensity of corresponding H35Cl and H37Cl isotopic lines from the natural abundance ratio. (It was shown, at the same time, that the isotopic reactions H + 35Cl2 → H35Cl + 35Cl and H + 37Cl2 → H37Cl + 37Cl have the same rate constant, within ±10%). A third method of measuring the extent of self-absorption, which depends on the detection of an anomaly in the relative intensity of P- and R-branch emission lines is discussed.The self-absorption method was applied to the study of the hydrogen–chlorine system in the 1–2 mm Hg pressure range (see also Part I). Mean partial pressures of HClν=0 ~ 10−2 mm Hg were measured in individual rotational states to an accuracy of ca. ±10%, using an optical path length of 20 cm. The rotational distribution in ν = 0 corresponded to a temperature of 1150 ± 150 °K (the uncertainty in this figure encompasses two independent methods of estimating the self-absorption), as compared with 1300 ± 100 °K for all vibrationally excited states (Part I).

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

10.26434/chemrxiv.7860023 ◽

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

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 1nOπ* state, and a receiver triplet state within 200 fs. The receiver state internally convert to the long-lived 3ππ* 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.

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The Microwave Spectrum of 3,4-Dihydro-1,2-Pyran

Zeitschrift für Naturforschung A ◽

10.1515/zna-1985-0909 ◽

1985 ◽

Vol 40 (9) ◽

pp. 913-919

Author(s):

Juan Carlos López ◽

José L. Alonso

Keyword(s):

Dipole Moment ◽

Excited States ◽

Ground State ◽

Principal Axis ◽

Microwave Spectrum ◽

Average Intensity ◽

Ring Conformation ◽

Vibrationally Excited ◽

Rotational Constants ◽

Displacement Measurements

Abstract The rotational transitions of 3,4-dihydro-1,2-pyran in the ground state and six vibrationally excited states have been assigned. The rotational constants for the ground state (A = 5198.1847(24), B = 4747.8716(24) and C = 2710.9161(24) have been derived by fitting μa, μb and μc-type transitions. The dipole moment was determined from Stark displacement measurements to be 1.400(8) D with its principal axis components |μa| =1.240(2), |μb| = 0.588(10) and |μc| = 0.278(8) D. A model calculation to reproduce the ground state rotational constants indicates that the data are consistent with a twisted ring conformation. The average intensity ratio gives vibrational separations between the ground and excited states of the ring-bending and ring-twisting modes of ~ 178 and ~ 277 cm-1 respectively.

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Microwave Spectra of Furazan. III. Rotation Spectra of Vibrationally Excited States

Zeitschrift für Naturforschung A ◽

10.1515/zna-1990-9-1009 ◽

1990 ◽

Vol 45 (9-10) ◽

pp. 1117-1130

Author(s):

Otto L. Stiefvater

Keyword(s):

Excited States ◽

Heterocyclic Compound ◽

Microwave Spectroscopy ◽

Vibrational Modes ◽

Vibrationally Excited ◽

Rotational Constants ◽

Rotational Spectra ◽

Microwave Spectra

Abstract The pure rotational spectra of molecules in 21 vibrationally excited states of the heterocyclic compound furazan (C2H2N2O) have been detected and studied by DRM microwave spectroscopy. Rotational parameters are reported for the 12 fundamental levels below 1500 cm-1 , and the contri-butions from 10 vibrational modes to the effective rotational constants and to the inertia defect of furazan are calculated.

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Relative Intensity Measurements in Microwave Spectroscopy

Review of Scientific Instruments ◽

10.1063/1.1718618 ◽

1963 ◽

Vol 34 (8) ◽

pp. 901-907 ◽

Cited By ~ 211

Author(s):

Alan S. Esbitt ◽

E. Bright Wilson

Keyword(s):

Relative Intensity ◽

Microwave Spectroscopy ◽

Intensity Measurements

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Microwave Spectrum of Cyclohexene Sulfide

Canadian Journal of Chemistry ◽

10.1139/v73-080 ◽

1973 ◽

Vol 51 (4) ◽

pp. 529-532 ◽

Cited By ~ 9

Author(s):

R. Kewley

Keyword(s):

Excited States ◽

Relative Intensity ◽

Vibrational State ◽

Heavy Atom ◽

Microwave Spectrum ◽

Cyclohexene Oxide ◽

Rotational Constants ◽

Ground Vibrational State ◽

Intensity Measurements

The microwave spectrum of cyclohexene sulfide (7-thiabicycIo[4,1,0]heptane) has been investigated in the 26.5–40 GHz region. R-branch lines due to both a- and c-type transitions have been assigned for the ground vibrational state and for the first excited states of the ring bending and ring twisting modes. From relative intensity measurements the frequencies of these two modes are estimated as: vbend = 115 ± 20 cm−1 and vtwist = 200 ± 60 cm−1. The rotational constants for the ground vibrational state are (in MHz): A = 3512.086 ± 0.010, B = 2057.969 ± 0.003, and C = 1623.023 ± 0.003. These values are consistent with a twisted half chair structure for the heavy atom skeleton of cyclohexene sulfide, similar to that of cyclohexene oxide.

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