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1.
Individual rovibronic transitions are isolated at high resolution from a crowded absorption feature with a fluorescence excitation technique which is based on detection of fluorescence from one and only one rovibronic level. The method is illustrated by resolving four rovibronic transitions from the single rotational line-like feature in the 0, 0 band of the (S1 ← S0) absorption of glyoxal vapor. The rotational structure of the 510 fluorescence band is studied as a function of tuning a narrow-band laser line (linewidth < 10?4 cm?1) to various positions in and near this absorption feature. The fluorescence structure proves an extremely sensitive tool for detecting small absorptions, with emission from 12 rovibronic levels being identified. One of the spectra so obtained is a close approximation of true single rotational level fluorescence. 相似文献
2.
The two-photon excitation spectrum of fluorobenzene vapor has been recorded in the region of the transition. The spectrum shows considerable rovibronic structure with the bulk of the intensity lying in the subsystem induced by the ν14(b2) vibration. Two types of rovibronic contours, arising from ΔKa = ±1 and from ΔKa = 0, ±2 transitions, are identified. Major features in these contours are assigned by comparison with synthetic spectra, calculated using known upper and lower state rotational constants. The intensity distribution among the various bands in progressions of the totally symmetric vibrations is considerably different from that in the one-photon absorption spectrum, and the possible reasons for this are discussed. 相似文献
3.
The two-photon excitation (TPE) spectrum of sulfur dioxide is reported in the region of the transition. The spectrum shows considerable rovibronic structure; the band contours are identified as arising from ΔK?1 = ± 1 transitions and rotational features are assigned by comparison with synthetic spectra generated from known rotational constants. The vibronic structure observed in TPE is quite similar to that observed in the one-photon spectrum: no zero-rank tensor transitions to levels with odd v3 are identified, though they are allowed in the presence of vibronic coupling. The vibronic intensity distribution in the TPE spectrum below the dissociation limit is similar to that in one-photon absorption. However, near the dissociation threshold (5.63–5.67 eV), marked intensity redistribution occurs, from which it is concluded that the lowest energy photo-dissociation process proceeds through asymmetric stretching of the SO bonds. 相似文献
4.
Keiji Matsumura Kentarou Kawaguchi Keiichi Nagai Chikashi Yamada Eizi Hirota 《Journal of Molecular Spectroscopy》1980,84(1):68-73
The v = 1 ← 0 vibration-rotation bands of the NS radical in the and electronic states were observed by using a tunable diode laser. From the least-squares analysis the band origins were determined to be 1204.2755(12) and 1204.0892(19) cm?1, respectively, for and . The rotational and centrifugal distortion constants and the internuclear distance in the X2Π electronic state were obtained as follows: Be = 0.775549(10) cm?1, De = 0.00000129(33) cm?1, and , with three standard deviations indicated in parentheses. 相似文献
5.
Although is forbidden in near case c molecules the A′ ← X transition can be efficiently accomplished by the three-step sequence . Transitions to a range of levels of A′, vA′ = 2–38, have been recorded by this means, using J-selective polarization-labeling spectroscopy. Principal constants of the A′ state of I35Cl are Te = 12682.05, ωe = 224.57, ωeχe = 1.882, ωeye = ?0.0107, Be = 0.08653, and αe = 0.000675 cm?1. The A′ state is therefore similar in its physical characteristics to two other (relatively) deep states, and , of the 2431 configuration. 相似文献
6.
Some spectroscopic properties of the low-energy electronic states of 9-fluorenone have been examined. The spectra in paraffin matrices at 4.2°K show detailed vibrational spectra. Two fluorescence spectra are observed; a diffuse emission arises from 9-fluorenone crystals in the paraffin matrix, and a sharp emission is characteristic of the molecule. The sharp fluorescence is analyzed in terms of known a1 vibrational fundamentals. The sharp absorption is a near mirror-image to the fluorescence, so Herzberg-Teller vibrations are not prominent. The polarization in the crystal spectrum allows this low-energy transition near 23 000 cm?1 to be assigned . Because there is no vibronic perturbation in fluorescence, and certainly no out-of-plane modes, a transition seen at about 26 000 cm?1 is tentatively assigned . Another sharp absorption system is seen at 31 000 cm?1 in the paraffin matrices at 4.2°K (linewidth 6 cm?1) but no fluorescence was detected. The polarized crystal spectrum indicated the assignment of this system and another very strong system at 40 000 cm?1 to be , while other systems at about 34 000 cm?1 and 44 000 cm?1 are .The phosphorescence spectrum of pyrene-d10 held in a single crystal of 9-fluorenone at 4.2°K has been recorded. No delayed fluorescence from the host crystal is observed at 4.2°K but is intense at 77°K. The energy difference between host and guest triplet levels is estimated to be about 900 cm?1 allowing the lowest triplet state of 9-fluorenone to be placed at 17 800 cm?1. 相似文献
7.
A correlation of spectroscopic data with all-valence-electron, results has been performed for a number of mono- and disubstituted benzenes containing nitro and/or amino groups. The lowest energy transitions of p-nitroaniline are predicted to be 11B1 ← 11A1, 21A1 ← 11A1, and 21B1 ← 11A1, in the order of increasing energy. These three transitions are assigned to (i.e., are encompassed within) the lowest energy absorption band envelope of p-nitroaniline. The lowest energy predicted transition of o- and m-nitroanilines is 2A′ ← 1A′ and is supposed to correspond to the totality of the lowest energy absorption feature in both of these systems. The orbital excitation nature of these transitions is discussed. 相似文献
8.
Laser-induced fluorescence excitation has been used to measure Stark splittings of selected lines in the and band systems of H2CS in electric fields up to 13 kV/cm. The derived excited state a-axis dipole moments are 0.820 ± 0.007 D for the 41 level of the 1A2 state; 0.838 ± 0.008 D for the zeroth vibrational level of 1A2; and 0.534 ± 0.015 D for the zeroth vibrational level of the 3A2 state. These results are compared with the corresponding values of H2CO, and interpreted in terms of the changing localization of the π and orbitals accompanying electronic excitation. 相似文献
9.
H.D. Bist J.C.D. Brand A.R. Hoy V.T. Jones R.J. Pirkle 《Journal of Molecular Spectroscopy》1977,66(3):411-420
The band system of NO2, , has been measured in absorption in a neon matrix at 6 K, using 15NO2 and N18O2 in addition to the normal isotope. The spectrum consists essentially of a single, long progression of bands terminating on successive levels of the bending mode in the upper state. Transitions to odd- and even-v2′ states occur with a uniform intensity distribution indicating that the rotation of the bent ground state of NO2 about its near-prolate axis is hindered in the matrix. The observations strongly suggest that the top axis of the molecule coincides with a C2 axis of neon crystals in the polycrystalline matrix. Relative to the vapor absorption the matrix spectrum is red shifted by about 150 cm?1, the crystal field parameter V2 and principal constants of the state of 14N16O2 in neon being 相似文献
10.
Nobukimi Ohashi Masao Kakimoto Shuji Saito Eizi Hirota 《Journal of Molecular Spectroscopy》1980,84(1):204-224
The vibronic transition (16 370 to 16 425 cm?1) of the DSO radical in studied by Doppler-limited dye laser excitation spectroscopy. DSO is produced in a flow system by reacting the products of a microwave discharge in O2 with D2S. About 637 observed lines are assigned to 987 transitions of the 19 subbands: K′a ← K″a = 6 ← 5, 5 ← 4, 4 ← 3, 3 ← 2, 2 ← 1, 1 ← 0, 0 ← 1, 1 ← 2, 2 ← 3, 3 ← 4, 0 ← 0, 1 ← 1, 2 ← 2, 3 ← 3, 4 ← 4, 3 ← 1, 2 ← 0, 0 ← 2, and 1 ← 3. They are analyzed to determine rotational constants, centrifugal distortion constants, and spin-rotation constants for both the ground and the excited electronic states. The band origin obtained is 16 413.874 (2.5σ = 0.002) cm?1. The rotational constants determined are combined with the previous result on HSO (M. Kakimoto et al., J. Mol. Spectrosc.80, 334–350 (1980)) to calculate the structural parameters for this radical in both the states: , , and ∠HSO = 106.6(5)° for the state, and , , and ∠HSO = 95.7(21)° for the state, where values in parentheses denote 2.5σ. 相似文献
11.
The electronic absorption spectra of thioformaldehyde and thioformaldehyde-d2 have been obtained. A vibrational analysis of the discrete band system in the 6100-4400-Å region is reported. The type A origin bands are at for , and are magnetic dipole allowed. The electronic transition is under the C2v point group. Most of the intensity of the system is in type B bands, and is due to vibronic mixing with higher 1B2 states when the inversion mode ν4 is excited. The molecule in the excited 1A2 state is “floppy-planar,” having a broad potential function with a barrier of the order of 20 cm?1 to the inversion motion. 相似文献
12.
Donald V. Brumbaugh Christopher A. Haynam Donald H. Levy 《Journal of Molecular Spectroscopy》1982,94(2):316-335
New fluorescence excitation and dispersed SVL fluorescence spectra of s-tetrazine vapor in supersonic expansions of helium and argon are reported. A forbidden in-plane-polarized component of the transition is discovered at (0, 0) + 578 cm?1 with a type-B band contour in rotationally resolved excitation spectra obtained with a single-frequency cw ring dye laser. Linewidth measurements of single rovibronic transitions provide data to calculate lifetimes of low-lying S1 vibronic states of the isolated molecule. Depending on the vibrational mode involved, the lifetime varies from 0.05 to greater than 1 nsec. The number of cold-band assignments in the absorption spectrum of s-tetrazine vapor now confirmed by analysis of SVL fluorescence spectra increases from three to ten. 相似文献
13.
Kohzo Hakuta 《Journal of Molecular Spectroscopy》1984,106(1):56-63
The vibration-rotation spectrum of the HCF molecule was observed by laser-induced fluorescence with an Ar+ laser. The laser line of 514.5 nm coincided with two rovibronic transitions, rR1(9) and pQ5(9) for . The spectrum consisted of the progression of bending vibrational mode ν2. The rotational lines were fully resolved for each of the vibronic bands. The analysis yielded the vibrational and rotational parameters for both the ground and the excited vibronic states. The rotational parameters of the state were obtained for four vibrational levels [(0v20), v2 = 0 – 3]. 相似文献
14.
Rydberg absorption series of N2 converging to the state of N2+ have been reinvestigated with a 6.65-m normal incidence vacuum spectrograph in the second order. Previously known A ← X series (I) and (II) have been extended to higher members with m ~ 40 and up to v′ = 7. 相似文献
15.
The cw dye laser excitation spectrum of the vibronic band of HCF was observed between 17 188 and 17 391 cm?1 with the Doppler-limited resolution, 0.04 cm?1. The HCF molecule was produced by the reaction of discharged CF4 with CH3F, and 853 lines were observed, of which 516 transitions were assigned to K′a ← K″a = 3 ← 4, 2 ← 3, 1 ← 2, 0 ← 1, 1 ← 0, 2 ← 1, 0 ← 0, 1 ← 1, 2 ← 2, 3 ← 3, 2 ← 0, and 0 ← 2 subbands. A rotational analysis yielded the rotational constants and quartic and sextic centrifugal distortion constants for both the and states and the band origin, with good precision. The molecular constants determined reproduce the observed transition frequencies with an average deviation of 0.0038 cm?1. Small rotational perturbations in the excited state were found at J = 5, 6 and J = 10, 11 of J1,J and at J = 15, 16 of J2,J?1 levels. 相似文献
16.
A weak emission spectrum of I2 near 2770 Å is reanalyzed and found to to minate on the A(1u3Π) state. The assigned bands span v″ levels 5–19 and v′ levels 0–8. The new assignment is corroborated by isotope shifts, band profile simulations, and Franck-Condon calculations. The excited state is an ion-pair state, probably the 1g state which tends toward . In combination with other results for the A state, the analysis yields the following spectroscopic constants: T″e = 10 907 cm?1, ″e = 1640 cm?1, ω″e = 95 cm?1, ; T′e = 47 559.1 cm?1, ω′e = 106.60 cm?1, . 相似文献
17.
The absorption spectrum of the 2491 Å NO2 bands () has been observed in neon and argon matrices at 6 K. Evidence for two distinct matrix sites is confirmed by the doubling of the electronic origin. The bands are shifted slightly to the blue (~ + 60 cm?1) in neon and to the red (~ ?64 cm?1) in argon. The excited state vibrational frequencies are reported. 相似文献
18.
J.A. Coxon 《Journal of Molecular Spectroscopy》1980,82(2):264-282
Literature data for the line frequencies of the B3Π(0u+) ← X1Σg+ transition of Cl2 are fitted directly by least squares to obtain new molecular constants. The constants from individual bands are merged to obtain single-valued estimates of the rotational constants for each vibrational level of the B state. The results are combined with recent data from the B → X system in emission to obtain new RKR turning points for the B and X states, and Franck-Condon factors for the B-X system. The new constants are also used to provide revised long-range parameters for Cl2(B) which differ from those of earlier work. In particular, the coefficient C5 of the leading term in the inverse-power long-range potential is now found to be . Theoretical results for the variation of centrifugal distortion parameters for levels near dissociation are tested for Dv and Hv, and an extrapolation based on this behavior is used to facilitate determination of reliable Bv and G(v) values for the highest observed B-state levels. 相似文献
19.
The flash photolysis of ClO2 has yielded a new absorption spectrum of ClO in the vacuum ultraviolet. Six electronic transitions have been assigned and vibrational constants for the upper states are given. All of the transitions are Rydberg in nature. The first four of these transitions are thought to be 2Σ ← X2Πi from which a spin-orbit coupling constant A = ?318 ± 5 cm?1 is obtained for the ground state.Hot bands in three of the above systems of ClO have been observed in absorption. This has enabled the direct measurement of the ground state vibrational constant (; ωe″ = 859 cm?1) for the first time.Extinction coefficients for a number of the ClO transitions have been measured. 相似文献
20.
The results of a vibrational and rotational analysis of the banded transition in are presented. Only three of the six vibrational modes are active in the spectrum with , , and . The spin forbidden transition gains intensity primarily by a mixing of the and states. This is confirmed by a rotational analysis of the 000 band of both isotopes. The rotational analysis shows that the coupling in the state is near Hund's case b and that the spin constants are nearly 10 times greater than those observed for CH2O. A calculation shows that this difference is due to the greater spin orbit coupling of S in CH2S and to the smaller energy differences between the , , , and the states. The r0 structure calculated from the rotational constants is , , βHCH = 119.6°, and α (out of plane) = 16.0°. A simultaneous fit of the vibrational levels in ν′4 of CH2S and CD2S to a double minimum potential function yielded a barrier to molecular inversion of 13 cm?1 and an equilibrium out-of-plane angle of 15°. 相似文献