Vibronic structure induced in spin-forbidden transitions in emission and absorption spectra by excited-state coupling

1992 ◽  
Vol 96 (22) ◽  
pp. 8757-8765 ◽  
Author(s):  
David Wexler ◽  
Jeffrey I. Zink ◽  
Christian Reber
Keyword(s):  
Excited State ◽  
Absorption Spectra ◽  
Vibronic Structure ◽  
Emission And Absorption Spectra ◽  
Forbidden Transitions

n–π* Electronic Emission and Absorption Spectra of o-Fluorobenzaldehyde in Vapor Phase

1970 ◽  
Vol 24 (1) ◽  
pp. 36-41 ◽  
Author(s):  
M. P. Srivastava ◽  
I. S. Singh
Keyword(s):  
Absorption Spectrum ◽  
Excited State ◽  
Emission Spectrum ◽  
Absorption Spectra ◽  
Vapor Phase ◽  
Ground State ◽  
Emission And Absorption Spectra ◽  
Quartz Spectrograph

The electronic emission and absorption spectra of o-fluorobenzaldehyde have been studied. The emission spectrum recorded on a Fuess glass and a medium quartz spectrograph lies in the region 26 668–17 862 cm−1 and the absorption spectrum recorded on a Zeiss Q–24 medium quartz spectrograph lies in the region 30 995–24 610 cm−1. The O—O band has been observed at 26 337 cm−1. The C=O stretching frequency 1733 cm−1 in the ground state and 1355 cm−1 in the excited state is most intense and forms progressions of bands both in the emission and absorption spectra. The observed bands have been interpreted as combinations of the C=O stretching frequency and its multiples with other fundamentals. The transition involved is A‘–A’ ( n–π*).

The electronic absorption spectra of NH 2 and ND 2

1959 ◽  
Vol 251 (1002) ◽  
pp. 553-602 ◽  
Keyword(s):  
Excited State ◽  
Bond Length ◽  
Absorption Spectra ◽  
Flash Photolysis ◽  
Electronic Absorption Spectra ◽  
Interaction Constant ◽  
Bending Vibration ◽  
Vibronic Structure ◽  
Linear Configuration ◽  
Centrifugal Distortion Constants

The absorption spectra of <super>14</super>NH 2 , <super>15</super>NH 2 and <super>14</super>ND 2 have been photographed in the region 3900 to 8300 A with a 21 ft. concave grating spectrograph. The radicals are produced by the flash photolysis of <super>14</super>NH 3 , <super>15</super>NH 3 and <super>14</super>ND 3 respectively. A detailed study of the <super>14</super>NH 2 - <super>15</super>NH 2 isotope shifts suggests that the molecule has a linear configuration in the excited state and that the spectrum consists of a long progression of the bending vibration in this state. These conclusions have been confirmed by detailed rotational and vibrational analyses of the 14NH2 and 14ND2 spectra. The spectra consist of type C bands for which the transition moment is perpendicular to the plane of the molecule. For NH2, sixteen bands of the progression (0, v'%, 0) <- (0, 0, 0) have been identified with v'% — 3, 4, ..., 18. In addition four bands of a subsidiary progression (1, v'2, 0) <- (0, 0, 0) have been found; these bands derive most of their intensity from a Fermi-type resonance between (0, v'2) 0) and (1, v2 —4, 0) levels in the excited state. The interaction constant W nl is 72 + 3 cm <super>-1</super>. For ND 2 , fourteen bands of the principal progression (v2 — 5 to 18) and one band of the subsidiary progression have been identified. The upper state vibration frequencies w?' and (i)' are 3325 cm <super>-1</super> and 622 cm <super>-1</super> for NH 2 and 2520 cm <super>-1</super> and 422 cm <super>-1</super> for ND 2 respectively. The bending frequencies are unusually low ; moreover, the anharmonicities of the bending vibration are unusually large and negative (x22—11.4 cm <super>-1</super> for NH 2 and 8.1 cm <super>-1</super> for ND 2 ). The origin of the system lies in the region o f 10000 cm <super>-1</super>. Ground-state rotational term values have been derived from observed com bination differences; values for the rotational constants Aooo, B'ooo and Cooo and for the centrifugal distortion constants D"A, D"b and D"0 have been determined. The bond lengths and bond angles for NH 2 and ND 2 agree and are 1.024 + 0.005 A and 103° 20' + 30' respectively. Small spin splittings have been observed. In the excited state an unusual type of vibronic structure has been found. Successive levels of the bending vibration consist alternately of 27, d , T, ... and ... vibronic sub-levels with large vibronic splittings. The origins of the vibronic sub-bands may be represented by the formula yf = Vq—GK2, where G is ~ 27 cm -1 for NH 2 and ~ 19 cm <super>-1</super> for ND 2 . The rotational levels show both spin and A-type doubling. No simple formula has been found to fit the energies o f the II, A, 0 and -T rotational levels; the 27 levels fit the formula F(N) = 1) — D N2(N + 1)2, though with a negative value for D . By extrapolating the B values for the 27 levels to = 0 we obtain B'00o = 8.7 8 cm <super>-1</super> for NH 2 and 4.4 1 cm<super>-1</super> for ND 2 . These values are consistent with a linear configuration with a bond length of 0.97 5 A. The significance of this short bond length is discussed. An explanation of the complex vibronic structure is given. The two combining states are both derived from an electronic II state which is split by electronic-vibrational coupling for the reasons advanced by Renner. A detailed correlation diagram is given. A quantitative treatment of this effect by Pople & Longuet-Higgins gives good agreement with the experimental data.

n–π* Electronic Emission and Absorption Spectra of p-Fluorobenzaldehyde Vapor

1972 ◽  
Vol 26 (2) ◽  
pp. 278-282 ◽  
Author(s):  
M. P. Srivastava ◽  
I. S. Singh
Keyword(s):  
Excited State ◽  
Absorption Spectra ◽  
Vapor Phase ◽  
Infrared Spectra ◽  
Emission And Absorption Spectra ◽  
Stretching Vibration

The n–π* electronic emission and absorption spectra of p-fluorobenzaldehyde have been studied in vapor phase. Its Raman and infrared spectra have also been recorded. The spectra have been analyzed in terms of several ground and excited state fundamental vibrations. The C=0 stretching vibration is quite intense and dominates both the spectra. The transition has been ascribed to either A′- A′ or A′-A″ ( n–π*).

X-ray emission and absorption spectra of carbon nitride films prepared by laser ablation

1999 ◽  
Vol 28 (6) ◽  
pp. 509-514 ◽  
Author(s):  
H. Izumi ◽  
T. Kaneyoshi ◽  
T. Ishihara ◽  
H. Yoshioka ◽  
H. Matsui ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Absorption Spectra ◽  
Carbon Nitride ◽  
X Ray ◽  
Emission And Absorption Spectra
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