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transition of 2,3-benzofluorene at low temperatures in the gas phase
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Image of FIG. 1.
FIG. 1.

Calculated PESs for the electronic states of Bzf as a function of the molecular geometry .

Image of FIG. 2.
FIG. 2.

Optimized geometry of benzofluorene in the electronic ground state (black) and modified geometry (gray/light blue). The corresponding potential energies are given in Fig. 1.

Image of FIG. 3.
FIG. 3.

absorption spectra of Bzf measured in a supersonic jet by CRDS (a) and in Ar matrices by conventional absorption spectroscopy (Ref. 17) (b) or by site-selective fluorescence (Ref. 16) (c). Bands labeled with a star are presented in more detail in Fig. 4. Note that the lower frame has been shifted by to higher wave numbers to account for the matrix shift.

Image of FIG. 4.
FIG. 4.

Close-ups of the bands labeled with a star in Fig. 3. The relative positions with respect to the origin band are given in the figure. Except for the temperature ( for the origin band and for the others), the experimental parameters were the same. Simulated (dotted) and synthetic (dashed) profiles are shown in (a) (see text). In (c) and (d), vertical lines indicate the centers of overlapping bands as determined by the simulations (dashed lines).

Image of FIG. 5.
FIG. 5.

Temperature study of the bands at (left) and (right) relative to the origin band in the range between 200 and .

Image of FIG. 6.
FIG. 6.

Study of the band profile as a function of the distance in the jet. All bands were recorded at . The distance between the probing volume and the nozzle exit was varied between 4.5 and 19 mm.

Image of FIG. 7.
FIG. 7.

Comparison of the carrier gases argon and neon. The band at was absent when neon was used. Due to less efficient cooling, the origin band measured with neon at is somewhat broader than the respective band observed under otherwise identical conditions with argon.

Image of FIG. 8.
FIG. 8.

Calculated stick spectrum of the transition of Bzf taking the Herzberg–Teller correction into account [panel (a)]. The band intensities are given with respect to the origin band. Experimental spectrum of Fig. 3(a) scaled so as to show the band at with its relative intensity as determined in Fig. 6 [panel (b)]. In either spectrum, the vibrational shift is relative to the position of the origin band at .


Generic image for table
Table I.

Vibrational frequencies of the state of Bzf measured in the spectrum observed in a supersonic jet and in an Ar matrix. The results of the computational study are included for comparison.

Generic image for table
Table II.

Vibrational eigenfrequencies of modes obtained at the geometry on the PES , Huang–Rhys factors , Herzberg–Teller corrections , and ratios of the intensities of the fundamental vibronic bands to the origin band, given by . Modes with Huang–Rhys factors lower than 0.006 or with frequencies higher than have not been included.

Generic image for table
Table III.

Calculated excitation energies and oscillator strengths for the lowest singlet electronic states of Bzf. The calculations have been carried out at different geometries indicated in the second column. Measured values are included for comparison.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: S1←S0 transition of 2,3-benzofluorene at low temperatures in the gas phase