SPECTRA AND STRUCTURES OF THE FREE HSiCl AND HSiBr RADICALS

1964 ◽  
Vol 42 (3) ◽  
pp. 395-432 ◽  
Author(s):  
G. Herzberg ◽  
R. D. Verma
Keyword(s):  
Fine Structure ◽  
Band Structure ◽  
Excited States ◽  
Ground State ◽  
Electronic Transition ◽  
Flash Photolysis ◽  
Geometrical Structure ◽  
Lower State ◽  
Triplet Splitting ◽  
Singlet Transition

Intense spectra of HSiCl and HSiBr in the region 6000 to 4100 Å have been obtained in the flash photolysis of SiH3Cl and SiH3Br, both in absorption and in fluorescence. They consist of progressions of bands with very wide K structures and very narrow J structures. A detailed fine structure analysis of these bands has been carried out and the geometrical structure of the molecules in both the upper and the lower states has been established. For the lower state, probably the ground state of HSiCl, it is found that[Formula: see text]and similarly for HSiBr[Formula: see text]In the excited states the angles are appreciably larger (see Table XI).A striking feature of the band structure in both HSiCl and HSiBr is the occurrence of branches of subbands with ΔK = ± 2, in addition to those with ΔK = ± 1 and 0, and furthermore, the presence of a subband with K = 0 in the branch with ΔK = 0. These anomalies can be accounted for by the assumption that the electronic transition is a triplet–singlet transition, more specifically 3A″–1A′ (or possibly 1A′–3A″). However, no triplet splitting has been resolved in the spectrum.

SPECTRUM AND STRUCTURE OF THE FREE HNCN RADICAL

1963 ◽  
Vol 41 (2) ◽  
pp. 286-298 ◽  
Author(s):  
G. Herzberg ◽  
P. A. Warsop
Keyword(s):  
Fine Structure ◽  
Ground State ◽  
Electronic Transition ◽  
Flash Photolysis ◽  
Geometrical Structure ◽  
Transition Moment ◽  
Lower State ◽  
State Formula ◽  
Exact Position

A widely spaced perpendicular band at 3440 Å observed in the flash photolysis of diazomethane is ascribed to the free HNCN radical. The study of the fine structure of this band for HNCN, DNCN, and HNC13N has yielded information about the geometrical structure of the molecule in both the upper and lower (ground) state. For the lower state[Formula: see text]The N—C—N group is very nearly linear, but the exact position of the C atom on this line could not be determined. The electronic transition is of the type 2A′–2A″, the transition moment being perpendicular to the plane of the molecule.

A NEW BAND SYSTEM OF THE P2 MOLECULE ANALOGOUS TO THE LYMAN–BIRGE–HOPFIELD BANDS OF N2

1958 ◽  
Vol 36 (5) ◽  
pp. 565-570 ◽  
Author(s):  
A. E. Douglas ◽  
K. Suryanarayana Rao
Keyword(s):  
Excited States ◽  
Ground State ◽  
Singlet State ◽  
Band System ◽  
Excited Singlet State ◽  
Lower State ◽  
High Dispersion ◽  
Electron Configuration ◽  
Excited Singlet ◽  
New System

Five bands of a new band system of P2 have been photographed at high dispersion and analyzed. The upper state of the system is a 1П0 state and lies lower than any previously known excited singlet state. The lower state of the new system is the ground state of P2 and the analysis of the new bands has given improved constants for this state. The new system appears to be the analogue of the Lyman–Birge–Hopfield bands of N2. The electron configuration of the low excited states of P2 and of related molecules is discussed.

THE 2 700 Å BANDS OF THE N3 MOLECULE

1965 ◽  
Vol 43 (12) ◽  
pp. 2216-2221 ◽  
Author(s):  
A. E. Douglas ◽  
W. Jeremy Jones
Keyword(s):  
Fine Structure ◽  
High Resolution ◽  
Ground State ◽  
Flash Photolysis ◽  
Bond Distance ◽  
Absorption Bands

The 2 700 Å absorption bands found by Thrush in the flash photolysis of HN3 have been studied at high resolution. The rotational fine structure of the strongest band has been analyzed, and it has been shown that the bands arise from a [Formula: see text] transition of the N3 molecule. The bond distance in the ground state of N3 is found to be 1.181 Å.

THE ABSORPTION SPECTRUM OF THE Si2 MOLECULE

1963 ◽  
Vol 41 (1) ◽  
pp. 152-160 ◽  
Author(s):  
R. D. Verma ◽  
P. A. Warsop
Keyword(s):  
Absorption Spectrum ◽  
Dissociation Energy ◽  
Ground State ◽  
Flash Photolysis ◽  
Lower State ◽  
The Third ◽  
Photolysis Apparatus ◽  
Vibrational Constants

Three band systems of Si2 have been found in absorption with a flash photolysis apparatus. Two of the band systems at 3200 and 2100 Å are new, whereas the third is an extension of the 3Σ–3Σ system observed by Douglas in emission. All three systems have the same lower state and arise from [Formula: see text] transitions. It is very probable that the [Formula: see text] state is the ground state of the Si0 molecule. Rotational and vibrational constants of all four 3Σ states have been determined. The dissociation energy of Si2 is estimated to be 3.0 ± 0.2 ev.

Rotational Structure in Some Higher Excited States of the GeF Molecule

1974 ◽  
Vol 52 (15) ◽  
pp. 1458-1475 ◽  
Author(s):  
R. W. Martin ◽  
A. J. Merer
Keyword(s):  
Emission Spectrum ◽  
Excited States ◽  
Ground State ◽  
Valence State ◽  
Rydberg States ◽  
The Other ◽  
Electronic Transitions ◽  
Lower State ◽  
High Dispersion ◽  
Higher Excited States

The weaker electronic transitions in the region 2000–9000 Å in the emission spectrum of GeF have been photographed at high dispersion; three new transitions with the A2Σ+ state as lower state have been discovered, and the various systems near 2100 and 8600 Å have been reassigned. The spectra have been explained in terms of six excited states lying between 40 000 and 50 000 cm−1 above the ground state, and representative bands involving all six have been analyzed rotationally. Five of these excited states are Rydberg states (5pσ, 5pπ, 4dπ, 4dδ, and 6sσ), and the other is the σπ22Δ valence state; this latter interacts strongly with the 4dδ 2Δ state.

The spectrum and structure of the free BH 2 radical

1967 ◽  
Vol 298 (1453) ◽  
pp. 142-159 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Excited State ◽  
Ground State ◽  
Electronic Transition ◽  
Flash Photolysis ◽  
Molecular Constants ◽  
Isotope Shifts ◽  
Geometrical Data

A new absorption spectrum has been found in the flash photolysis of H 3 BCO which, from its structure and the observed isotope shifts can be unambiguously assigned to the free BH 2 radical. The spectrum represents a transition similar to those previously observed in NH 2 and CH 2 . The molecule is linear in the excited state but bent (with an angle of 131°) in the ground state. Molecular constants and geometrical data are evaluated. The electronic transition is 2 B 1 ( II u ) – 2 A 1 and fits well with expectation from the Walsh diagram for X H 2 molecules.

ROTATIONAL ANALYSIS OF THE γ SYSTEM OF THE PO MOLECULE

1958 ◽  
Vol 36 (11) ◽  
pp. 1526-1535 ◽  
Author(s):  
K. Suryanarayana Rao
Keyword(s):  
Ground State ◽  
Electronic Transition ◽  
Lower State ◽  
High Dispersion ◽  
Rotational Analysis ◽  
Small Perturbations ◽  
Rotational Constants ◽  
The One

The bands of the γ system of the PO molecule have been photographed under high dispersion (0.35 Å/mm). A rotational analysis of the 0–0, 0–1, and 1–0 bands is given, which differs from the one previously given by Sen Gupta. In addition, four more bands, namely, the 1–2, 2–1, 2–3, and 2–4 bands, have been analyzed. The bands are attributed to the electronic transition, A3Σ–X2Πreg, the lower state being the ground state of the molecule. The new rotational constants for the ground state are the following:[Formula: see text]The spin doubling in the upper state is small. Perturbations in the v = 0 level of the upper state, which were not reported previously, are observed and discussed. They supply a welcome confirmation of the correctness of the analysis here presented.

THE ABSORPTION SPECTRUM OF SH AND SD IN THE VACUUM ULTRAVIOLET

1966 ◽  
Vol 44 (10) ◽  
pp. 2447-2459 ◽  
Author(s):  
B. A. Morrow
Keyword(s):  
Absorption Spectrum ◽  
Excited State ◽  
Excited States ◽  
Ground State ◽  
Vacuum Ultraviolet ◽  
Flash Photolysis ◽  
Electronic States ◽  
Rydberg Series ◽  
A Value ◽  
Vibrational Constants

The absorption spectrum of SH in the vacuum ultraviolet has been obtained by the flash photolysis of hydrogen sulfide. Transitions from the 2Π ground state to seven excited states have been observed and four of these fit reasonably well into a Rydberg series. From an extrapolation to the convergence limit of this series, a value of 10.40 ± 0.03 eV for the ionization potential of SH has been derived. Values for the rotational constants of these new electronic states have been determined; corresponding data for SD have also been obtained. The (1–0) transition of the system near 1 670 Å (B2Σ–X2Π) was observed, and, with the aid of isotope relations, vibrational constants of the B state have been derived. An estimate of the dissociation energy of SH in this excited state is D0′ = 24 190 ± 1 000 cm−1.

Theoretical study of the vibrational structure of the 1(n,π*) transition in diimide: potential curves and Franck–Condon analysis

1977 ◽  
Vol 55 (9) ◽  
pp. 1533-1545 ◽  
Author(s):  
M. Perić ◽  
R. J. Buenker ◽  
S. D. Peyerimhoff
Keyword(s):  
Band Structure ◽  
Excited States ◽  
Electronic Transition ◽  
Isotope Shift ◽  
Theoretical Study ◽  
Vibrational Structure ◽  
Absorption System ◽  
Electronic Transition Moment ◽  
Franck Condon ◽  
Potential Curves

Ab initio CI potential curves are reported for the ground and 1(n,π*) excited states of diimide for each of the six possible internal coordinates. These results are then used to obtain vibrational wavefunctions and frequencies for both states, which in turn are combined with electronic transition moment data to allow a Franck–Condon analysis of the band structure of the (dipole-forbidden) n–π* absorption system. This procedure allows one to reproduce the main features of the observed spectra of N2H2 and N2D2 and indicates that the majority of the vibrational transitions seen are vibronically induced via the antisymmetric NH stretching mode v5. The calculations are in essential agreement with the earlier experimental interpretation of the vibrational structure of this transition in terms of progressions in the symmetric bending (v2) and NN stretching (v3) frequencies, except that they indicate that the previous v2′ numbering should be altered by three units. According to this interpretation the isotope shift for the vibronic origin is 672 cm−1 compared with the corresponding calculated value of 666 cm−1. It is argued that several other weaker transitions seen experimentally arise via a different inducement mechanism, namely the torsion (v4) mode, and as such are only observed in energy regions where v5-induced transitions cannot occur.

Sign in / Sign up

Export Citation Format

Share Document