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Electronic spectroscopy of I2–Xe complexes in solid Krypton
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View: Figures


Image of FIG. 1.
FIG. 1.

Gas-phase potentials of I2 that are relevant for this study. Panel (a) depicts the potentials that are important in VUV absorption of solid I2/Xe/Kr ternary systems. Position of the VUV absorption in solid Kr and the effects caused by Xe are also indicated in the picture. Panel (b) shows the relevant I2 potentials in emission. Transitions observed in this study with 193 nm excitation of mixed Kr/Xe matrices are also indicated with the colored arrows. Two possible multiphoton excitation routes and the corresponding I2 potentials in pump-probe emission are shown in the panel (c). The shown potentials in the panel (c) relate to excitation with two femtosecond laser pulses centered at λ Pump = 558 nm and λ Probe = 620 nm, as will be discussed in the Sec. III C. The potentials in the Figure 1 have been constructed from multiple different sources (Refs. 1–6 and the references therein).

Image of FIG. 2.
FIG. 2.

VUV/UV absorption spectra of I2 in pure krypton (Xe = 0%), in xenon doped krypton (Xe = 0.1–4.0%), and in pure xenon (Xe = 100%). All the spectra have been recorded at 40 K and normalized to respective absorption maxima. Spectrum labels denote xenon pressure percentage in the gaseous host matrix (Xe = p(Xe)/(p(Kr) + p(Xe)) * 100%). I2/Rg (Rg = Kr + Xe) ratio was ∼1/2600 in all experiments. For explanation of different patterns in the picture, see text.

Image of FIG. 3.
FIG. 3.

Emission spectra of I2 obtained after 193 nm excitation in pure krypton (Xe = 0%, black spectrum), and in slightly Xe doped krypton (Xe = 0.1%–2%, color coded spectra) matrices at 19 K. All spectra are normalized to UV transition shown in the grey inset (a), where the tentatively assigned F → a transition is slightly offsetted for clarity. Thus, the spectra in the main picture and inset (b), represent changes of emission relative to the F → a transition. Tentative assignments of other ion-pair emissions are indicated in the picture. Note that the spectra are composition of two different measurements, one in the UV-region with a very short time gate (gate width 20 ns), and one in the visible region with a long time gate (gate width 6 μs). Different measurements are separated in the picture with black vertical line. A fixed time delay of t was used in all measurements. In the pure krypton case both regions have been measured with a same gate width of 10 μs. The spectra are uncorrected for spectral response of the detection system.

Image of FIG. 4.
FIG. 4.

Spectral changes of I2 main emission upon Xe doping of Kr matrix at 19 K. Panel (a) shows the normalization to center of emission at 24 000 cm−1. Panel (b) shows the difference between normalized Xe doped emissions vs. emission in pure krypton. Color coding in the panel (b) relates to the Xe doping ratio in the panel (a). In the bottom panel the spectrum with certain color is the top panel spectrum with the same color minus the spectrum in pure Kr (black spectrum in panel (a)). The shown spectra are the same as shown in Figure 3 with short time gating and different normalization.

Image of FIG. 5.
FIG. 5.

Spectral changes of I2 emission in the visible doublet region upon Xe doping of Kr matrix at 19 K. Panel (a) shows the emissions normalized at 15 900 cm−1 with gate delay of t. Panel (b) shows the same spectra with a larger time gate delay of t + 200 ns. Normalization constant used in the panel (a) has been used in the panel (b). The spectra have been measured with same gate widths as the visible region in Figure 3 (10 μs for I2/Kr and 6 μs for the Xe doped).

Image of FIG. 6.
FIG. 6.

Emission spectra of I2 with 193 nm excitation from pure krypton (Xe = 0%), to pure Xe, at 19 K. Panel (a) shows the measured spectra from UV-region to visible region. The shown spectra are again composition of two measurements, but in this case the both regions have been measured with long time gate width of 10 μs, except for the Xe = 2.0%, where the parameters used were 200 ns for the UV-region, and 6 μs for the visible region. Spectra have been normalized to the maxima of the main emission in the 26 000–23 000 cm−1 region and offsetted for clarity. Panel (b) is an enlargement of the visible region. Presumed origin of the different transitions is indicated in the picture. The spectrum Xe = 100% contains presumably an artifact emission marked with an asterisk. The shape and the energy implies that emission is a second order diffraction of the continuum-type of emission with a maximum at 26 500 cm−1.

Image of FIG. 7.
FIG. 7.

Top panel is a pump-probe emission contour of I2/Kr matrix with 0.1% of Xe at T = 10 K, where λ Pump = 558 nm and λ Probe = 620 nm. Contour has been measured with fast gating (60 ns). Intensity (z-axis) is normalized to the maximum of the main emission at t = 0 ps. Normalized intensity is shown in logarithmic scale to highlight weak emissions in the positive time delays. Lower panels (a) and (b) show spectral cuts measured at probe delays = ±3 ps for matrix without Xe and with 0.1% of Xe. Individual transitions have been highlighted in the spectra of Xe = 0.1%. Lower panels (c) and (d) shows the time evolutions of fitted areas of D → A and f → B emissions for matrices with Xe = 0% and Xe = 0.1%.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Electronic spectroscopy of I2–Xe complexes in solid Krypton