The magnetic rotation spectrum of formaldehyde: singlet–triplet perturbations in the 41 and 43 levels of the Ã1A2 state of H2CO

1979 ◽  
Vol 57 (8) ◽  
pp. 1224-1232 ◽  
Author(s):  
D. A. Ramsay ◽  
S. M. Till
Keyword(s):  
Absorption Spectrum ◽  
High Resolution ◽  
Rotational Level ◽  
Magnetic Rotation ◽  
Matrix Elements ◽  
Coriolis Interaction ◽  
Near Ultraviolet ◽  
The Matrix ◽  
Rotation Spectrum

A survey of the magnetic rotation spectrum (MRS) of formaldehyde in the near ultraviolet is reported. The [Formula: see text] and [Formula: see text] bands of the [Formula: see text] system are also studied under high resolution. The rR and pP branches of these bands are found to be active and it is noted that the intensities appear to increase more rapidly with increasing Ka in the MRS than in the absorption spectrum. The 43 and 61 levels are in Coriolis interaction at higher Ka values, and some rR branches of the [Formula: see text] band are identified.Several strong lines in the MRS are shown to be associated with rR, rP, pR, and pP lines in the absorption spectrum and to reveal the presence of singlet–triplet perturbations. Only one perturbed rotational level is found in the [Formula: see text] band, but for the [Formula: see text] band several rotational levels are found to exhibit such perturbations, e.g. 190,19, 191,19, 171,16, 102,8, 102,9, 112,9, 173,14, 173,15, 183,15, and 183,16. These perturbations are produced by ΔJ = ΔN = ΔKa = 0 interactions with the 415161 level of the ã3A2 state and by ΔJ = ΔN = 0. ΔKa = ± 1 interactions with the 5161 level. The matrix elements are of the order of 0.01–0.10 cm−1.

High-resolution Fourier transform study of the ν11 and ν7 fundamentals of cyclopropane

1984 ◽  
Vol 62 (12) ◽  
pp. 1369-1373 ◽  
Author(s):  
Josef Pliva ◽  
J. W. C. Johns
Keyword(s):  
Fourier Transform ◽  
High Resolution ◽  
Spectroscopic Constants ◽  
Hamiltonian Matrix ◽  
Matrix Elements ◽  
Vibrational States ◽  
Coriolis Interaction ◽  
Band Origin ◽  
The Matrix ◽  
Parallel Band

The absorption spectrum of cyclopropane, C3H6, was measured in the region between 790 and 950 cm−1 on a high-resolution Fourier transform spectrometer. The section containing the Q-branches of the perpendicular band of the ν11 vibration of species E′ was deconvolved to an effective line width of 0.0020–0.0025 cm−1. The structure of the ν11 band is strongly affected by l-type resonance. A total of 88 sub-bands with KΔK = −42 to 45 have been assigned in this band. The K = 4–3 and 2–3 sub-bands both exhibit K doubling of the lines with high J resulting from a combined effect of the off-diagonal matrix elements [Formula: see text], [Formula: see text], and [Formula: see text] with the l doubling in the K = 1, l = 1 state. Otherwise, the ν11 band is found to be free of perturbations by other vibrational states, in spite of the fact that a Jx,y Coriolis interaction is allowed by selection rules with the ν7 band (species [Formula: see text]) whose band origin is only 14.38 cm−1 below that of ν11. This shows that the value of [Formula: see text] is essentially zero. Also, the allowed Jz Coriolis interaction with the ν10 state, which lies 160.01 cm−1 above ν11, does not noticeably affect the two bands. A Hamiltonian matrix, including the matrix elements responsible for the K doubling and l-type resonance, was used for the treatment of the ν11 band. A set of accurate ground state constants and spectroscopic constants for the upper state ν11 is reported that reproduces 3240 observed lines of this band with a standard deviation of 0.0009 cm−1. Lines of the parallel band ν7 are just barely seen between the ν11 lines, which are perhaps 30–50 times stronger. Spectroscopic constants for the ν7 band have been obtained from 135 individual lines assigned to the Q- and R-branches of sub-bands with K = 6–21.

The magnetic rotation spectrum of formaldehyde: singlet–triplet perturbations in the 2141, 2143, 2243, and 2341 levels of the à lA2 state of H2CO

1983 ◽  
Vol 61 (1) ◽  
pp. 6-14 ◽  
Author(s):  
C. M. L. Kerr ◽  
D. C. Moule ◽  
D. A. Ramsay
Keyword(s):  
Magnetic Activity ◽  
Triplet States ◽  
Magnetic Rotation ◽  
Matrix Elements ◽  
Molecular Constants ◽  
Absorption Bands ◽  
Vibrational Assignments ◽  
The Matrix ◽  
Upper Level ◽  
Rotation Spectrum

The absorption spectra and magnetic rotation spectra of the [Formula: see text],[Formula: see text],[Formula: see text], and [Formula: see text] bands of the [Formula: see text] system of formaldehyde have been studied at high resolution. The earlier analyses of the absorption bands have been refined and improved molecular constants obtained. Several singlet–singlet perturbations have been noted and possible mechanisms discussed.The magnetic activity falls into two classes. Three of the bands show limited singlet–singlet activity with characteristics similar to those found earlier for the [Formula: see text] and [Formula: see text] bands. All the bands show singlet–triplet activity which is characterized by the appearance of rR, rP, pR, and PP transitions associated with a common upper level. Tables of perturbed excited-state singlet levels are given. No appreciable shifts of the perturbed levels have been found indicating that the matrix elements are small. For the [Formula: see text] band two perturbation mechanisms are proposed and the vibrational symmetries and energies of the perturbing triplet states are determined. The energies are too high to permit unambiguous vibrational assignments.

The magnetic rotation spectrum of thioformaldehyde: singlet–triplet perturbations in the Ã1A2 state

1982 ◽  
Vol 60 (9) ◽  
pp. 1212-1222 ◽  
Author(s):  
D. J. Clouthier ◽  
D. C. Moule ◽  
D. A. Ramsay ◽  
F. W. Birss
Keyword(s):  
High Resolution ◽  
Vibrational Level ◽  
Interaction Matrix ◽  
Magnetic Rotation ◽  
Matrix Elements ◽  
Selection Rules ◽  
Rotation Spectrum

Singlet–triplet perturbations in the [Formula: see text] and [Formula: see text] bands of the [Formula: see text], system of H2CS have been studied by high resolution absorption and magnetic rotation spectroscopy. Extensive perturbations in the [Formula: see text] band are associated with corresponding activity in the magnetic rotation spectrum. The shifts of the levels are consistent with interaction matrix elements up to ~ 1 cm−1. The selection rules indicate that the zeroth vibrational level of the 1A2 state is perturbed by the 4361 level of the 3A2 state. A number of perturbations are also observed in the [Formula: see text] band.

High resolution absorption spectrum of nitric oxide (NO) in the region of the first ionization limit

1976 ◽  
Vol 54 (20) ◽  
pp. 2074-2092 ◽  
Author(s):  
E. Miescher
Keyword(s):  
Absorption Spectrum ◽  
High Resolution ◽  
Ionization Energy ◽  
Dissociation Limit ◽  
Matrix Elements ◽  
Rydberg Series ◽  
Isotopic Species ◽  
Vibrational Levels ◽  
Energy Formula ◽  
Ionization Limit

The absorption spectrum of cold NO gas has been photographed at high resolution between 1400 and 1250 Å for two isotopic species. Resolved bands of the Rydberg series converging to vibrational levels of the 1Σ+ ground state of NO+ are studied. They include nf–X bands up to n = 15 and ns–X bands up to n = 11, all of which show sharp rotational structure. The higher members of the np–X series are generally very diffuse with only npσ being sufficiently sharp to show broadened rotational lines. Also mostly diffuse are the ndδ–X bands. The bands ndσ, π–X are not observed. The rapidly (n−3) narrowing structure of the nf complexes is discussed and the ionization energy [Formula: see text] accurately determined by extrapolation of selected rotational lines. Interactions between Rydberg states are numerous, s ~ d mixing produces a strong effect above n = 6 when (n + 1)s levels fuse with nl levels into 'supercomplexes'. Matrix elements are given for observed 8f ~ 9s and 6f ~ 6dδ interactions.Valence levels are not observed above the ionization energy, except for the repulsive state A′2Σ+ arising from the first dissociation limit and seemingly assuming Rydberg character at molecular internuclear distance. Observed anomalies are qualitatively discussed.

VACUUM-ULTRAVIOLET EMISSION AND ABSORPTION SPECTRUM OF THE NO MOLECULE: THE 2Δ STATES AND THEIR INTERACTIONS

1966 ◽  
Vol 44 (12) ◽  
pp. 3197-3216 ◽  
Author(s):  
Ch. Jungen
Keyword(s):  
Absorption Spectrum ◽  
Excited States ◽  
Vacuum Ultraviolet ◽  
Order Approximation ◽  
Electronic Configuration ◽  
Zero Order ◽  
Matrix Elements ◽  
Ultraviolet Emission ◽  
Zero Order Approximation ◽  
The Matrix

The emission spectrum of NO between 1 600 and 1 400 Å has been studied with a 1-m vacuum spectrograph. It consists of the two types of mutually perturbing 2Δ–X2Π bands already known from the much more complex absorption spectrum: the Rydberg systems F2Δ–X2Π, N2Δ–X2Π and the non-Rydberg system B′ 2Δ–X2Π. The interactions between the excited states of different electron configurations are of special interest. The matrix elements H = Hvib ∙ He have been obtained from detailed rotational analyses, a "deperturbation" in two steps has been carried out, and constants for the deperturbed 2Δ states are given. With calculated overlap integrals Hvib, the electronic configuration interaction energy He is derived. "Crossing" potential energy curves have been shown to be the appropriate zero-order approximation when [Formula: see text]. The phase of the interaction, i.e. the sign of He, has been deduced from the perturbed intensities of the observed bands.

Développement complet de l'hamiltonien de vibration–rotation adapté à l'étude des interactions dans les molécules toupies sphériques. Application aux bandes ν2 et ν4 de 12CH4

1977 ◽  
Vol 55 (20) ◽  
pp. 1802-1828 ◽  
Author(s):  
Jean-Paul Champion
Keyword(s):  
Ground State ◽  
Coupling Scheme ◽  
Order Of Approximation ◽  
Matrix Elements ◽  
Coupling Coefficients ◽  
Linear Combinations ◽  
Coriolis Interaction ◽  
Raman Transitions ◽  
The Matrix ◽  
Vibration Rotation

Using an unsymmetrized coupling scheme in the group Td, we determine all the vibration–rotation operators of the Hamiltonian of XY4 molecules, including all possible interactions, up to any order of approximation. We define a basis of Hamiltonian matrices of which the matrix elements are functions of coupling coefficients of the group chain [Formula: see text] only. Thus, we develop a general formalism available for any vibrational sublevels of whatever symmetry. The parameters relative to the different vibrational sublevels are known linear combinations of the coefficients of the Hamiltonian expansion. From these, we deduce simple relations between the parameters associated with the ground state, the fundamentals, and the harmonic and combination bands.We apply this formalism to the study of the Coriolis interaction between ν2 and ν4 of CH4. With only 21 parameters for the two bands, we obtain a standard deviation of 34 mK for 251 Raman transitions of ν2 and 20 mK for 243 ir transitions of ν4.

Magnetic Rotation and Absorption Spectra of cis and trans Acrolein

1971 ◽  
Vol 49 (21) ◽  
pp. 2710-2717 ◽  
Author(s):  
E. J. Bair ◽  
W. Goetz ◽  
D. A. Ramsay
Keyword(s):  
Absorption Spectrum ◽  
Absorption Spectra ◽  
Trans Isomer ◽  
Magnetic Rotation ◽  
A Cell ◽  
Reverse Situation ◽  
Cis And Trans ◽  
Rotation Spectrum

Six bands have been observed in the magnetic rotation spectrum of acrolein at 4040, 4069, 4122, 4178, 4220, and 4322 Å. The first five bands are assigned to the 3A″–1A′ (π*–n) transition of trans acrolein with the 0–0 band at 4122 Å. The sixth band at 4322 Å is assigned as the 0–0 band of the 3A″–1A′ (π*–n) transition of the cis (or gauche) isomer. The 3A″ state of the cis (or gauche) isomer lies below the corresponding state of the trans isomer by a similar interval to that found earlier for the 1A″ (π*–n) states. The reverse situation exists for the ground states.The absorption spectrum has also been reinvestigated using up to 30 m atm of gas in a cell heated to 180 °C. New assignments are given for some of the bands.

scholarly journals Coriolis perturbations in the methane spectrum. IV. Four general types of Coriolis perturbation

1939 ◽  
Vol 171 (947) ◽  
pp. 450-468 ◽  
Keyword(s):  
Rotational Quantum Number ◽  
Rotational Level ◽  
Theoretical Method ◽  
Matrix Elements ◽  
Infra Red ◽  
The Matrix ◽  
Coriolis Perturbation ◽  
Tetrahedral Molecule ◽  
New Perturbation ◽  
Degenerate Vibration

In previous papers (Jahn 1938, Childs and Jahn 1939) a new Coriolis perturbation in the methane spectrum was investigated. This perturbation arose from a coupling of the rotational levels of an infra-red active threefold degenerate vibration with those of an inactive twofold degenerate vibration. In the present paper, which is a continuation of this work, it is our purpose to show that in a regular tetrahedral molecule there are in all four possible distinct types of Coriolis perturbation. Two of these do not produce a splitting of the rotational levels but merely a displacement of the rotational level as a whole, whilst the other two produce a splitting as well as a displacement, one of these latter perturbations being identical with the type of perturbation previously investigated. General formulae are derived for the matrix elements of these new types of perturbation, and in the case of the new perturbation which produces a splitting of the levels, we factorize the perturbation matrices up to the tenth rotational quantum number, using the group-theoretical method previously developed. These results will be useful in elucidating the rotational structure of the overtones and combination tones of methane.

The Band System of Propynal: Rotational Analysis of the 0–0 Band Near 4145 Å

1973 ◽  
Vol 51 (17) ◽  
pp. 1810-1814 ◽  
Author(s):  
F. W. Birss ◽  
Ronald Y. Dong ◽  
D. A. Ramsay
Keyword(s):  
High Resolution ◽  
Band System ◽  
Transition Moment ◽  
Magnetic Rotation ◽  
Rotational Analysis ◽  
Molecular Constants ◽  
Rotation Spectrum

The 0–0 band of the [Formula: see text] system of propynal near 4145 Å has been photographed under high resolution and a rotational analysis carried out. The principal molecular constants for the ã3A″ state are (in cm−1):[Formula: see text]Altogether, 1237 lines have been assigned to transitions with ΔKa = 0. The dominant transition moment involves mixing of the ã3A″ state with higher 1A′ states.A simple magnetic rotation spectrum has been obtained and the assignments of the lines discussed.

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