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Demonstration and interpretation of significant asymmetry in the low-resolution and high-resolution Q y fluorescence and absorption spectra of bacteriochlorophyll a
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10.1063/1.3518685
/content/aip/journal/jcp/134/2/10.1063/1.3518685
http://aip.metastore.ingenta.com/content/aip/journal/jcp/134/2/10.1063/1.3518685

Figures

Image of FIG. 1.
FIG. 1.

Absorption (blue line) and fluorescence (red line) spectra of BChl a in TEA at room temperature. The fluorescence was excited at around 405 nm. The vertical lines label band positions in nanometers. The inset shows the overlap of the absorption and emission spectra in transition dipole moment representation (see text for details).

Image of FIG. 2.
FIG. 2.

Absorption (blue line) and fluorescence (red line) spectra of BChl a in predominantly (a) hexa- and (b) penta-coordinated TEA at 4.5 K. The fluorescence spectra were excited at around 405 nm. The rest as in Fig. 1.

Image of FIG. 3.
FIG. 3.

Comparison of the Q y and Q x band profiles in hexa-coordinated BChl a: TEA at (a) 295 and (b) 4.5 K.

Image of FIG. 4.
FIG. 4.

Typical ΔFLN spectra (red curves) of BChl a obtained at 4.5 K in (a) TEA at (excitation at 780.2 nm) and (b) 1-propanol (at 791.0 nm) matrixes. The black and blue curves show the corresponding pre- and post-burn FLN spectra recorded with lowburn fluencies of 0.20 and 0.15 mJ/cm2, respectively. The intermediate hole-burning fluencies were 4.6, and 3.2 mJ/cm2. The insets show the ΔFLN spectra exposing full ZPL intensities with a resolution of 8 cm−1.

Image of FIG. 5.
FIG. 5.

(a) Vibronic sideband of the ΔFLN spectrum of BChl a in TEA at 4.5 K obtained at 780.2-nm excitation. The numbers indicate the main vibrational frequencies in wave numbers. The modeled phonon wing is shown by the red curve. The lower blue curve is the difference between the above black and red curves offset for clarity. (b) Vibronic region of the ΔFLN spectra of BChl a in fivefold- and sixfold-coordinated TEA, in diethyl ether, and in 1-propanol at 4.5 K. Vertical lines indicate vibrational mode frequencies in wave numbers.

Image of FIG. 6.
FIG. 6.

Overlay of the CAM-B3LYP/6–311G* optimized geometries of the ground state (C cyan, N blue, H white, O red, Mg brown) and 1 Q y (green) excited state of Me-BChl a in the gas phase.

Image of FIG. 7.
FIG. 7.

Calculated absorption (blue solid) and reflected emission (red dashed) band profiles of Me-BChl a in the gas phase. The CAM-B3LYP/3–21G and CAM-B3LYP/6–31G* absorption and emission spectra were evaluated from displacement vectors at these levels of theory using normal modes similarly determined while the CAM-B3LYP/6–311G* displacements were projected onto CAM-B3LYP/6–31G* normal modes.

Image of FIG. 8.
FIG. 8.

Components of the homogeneous spectral profile retrieved from the ΔFLN measurements of BChl a in TEA. Assuming the experimentally limited bandwidth of ∼8 cm−1, the ZPL at zero frequency was cut off at ∼4.5% of its peak intensity. The peak of the IDF (green dashed line) at ω C = 12 852 cm−1 is set coinciding with zero frequency. The inset shows the approximated shape of the one-phonon profile.

Image of FIG. 9.
FIG. 9.

Comparison of the experimental (continuous lines) and convoluted (broken lines) absorption (blue and green) and fluorescence emission (red) spectra at 4.5 K. See text for details.

Image of FIG. 10.
FIG. 10.

Comparison of the BChl a mode structures in ΔFLN (black curve) and HB (turquoise histogram) spectra. The latter is built based on the data from Ref. 8. The numbers indicate the main vibrational frequencies in wave numbers.

Image of FIG. 11.
FIG. 11.

The points show, for the intense absorption line calculated at 1512 cm−1, the calculated contributions to the excited-state vibrational wavefunction (blue) and displacement (red) from each of the ground-state modes, while the corresponding continuous lines show the integrated contributions. Similar plots for 11 other modes are provided in supplementary material (Ref. 73).

Tables

Generic image for table
Table I.

Calculated (for Me-BChl a) and observed (for BChl a) reorganization energies (in cm−1) for Q y absorption (λ A ) and emission (λ E ).a

Generic image for table
Table II.

Dominant vibrational mode frequencies, ν j (±2 cm−1), Huang–Rhys factors, S j (±0.0005), and associated reorganization energies, λ j , in a selectively excited ΔFLN spectrum of BChl a in triethylamine at 4.5 K.

Generic image for table
Table III.

Comparison of observed [from ΔFLN and RR (Ref. 17)] to calculated (scaled CAM-B3LYP/6–31G*) vibrational frequencies and reorganization energies λ E of the strongest coupled modes (those calculated and/or observed with λ E > 3 cm−1).

Generic image for table
Table IV.

Comparison of observed[from HB experiments (Ref. 8) in glycerol/water/LDA) glass at 5 K] to calculated (scaled CAM-B3LYP/6–31G*) vibrational frequencies and reorganization energies λ A of the strongest coupled modes (those calculated and/or observed with λ A > 5 cm−1).

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/content/aip/journal/jcp/134/2/10.1063/1.3518685
2011-01-11
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Demonstration and interpretation of significant asymmetry in the low-resolution and high-resolution Qy fluorescence and absorption spectra of bacteriochlorophyll a
http://aip.metastore.ingenta.com/content/aip/journal/jcp/134/2/10.1063/1.3518685
10.1063/1.3518685
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