Scheme for detection of the double-minimum 3 3Π excited electronic state of KRb. The PA laser is detuned below the K(4s) + Rb(5p 1/2) asymptote by 43.82 cm−1. The resulting a 3Σ+ state molecules are then ionized via REMPI, where the 3 3Π state is the resonant intermediate state. Note that the previously analyzed 4 3Σ+ state occurs in the same region of the spectrum. 9,10
Plots of all available theoretical Hund's case (c) potentials arising from the K(4s) + Rb(4d) and K(4s) + Rb(6s) asymptotes. The Ω = 0+, 0−, 1, and 2 components are shown separately. In each case, the dashed line curve indicates the diabatic potential constructed to approximate the corresponding Ω component of the 3 3Π state. The inset in (a) shows an expanded view of a typical avoided crossing between adiabatic curves.
Modified potential energy curves showing the spin-orbit components of the 3 3Π state. The inset (a) shows the entire potential curves, while the main figure (b) shows an expanded view in which the Ω = 0, 1, and 2 components are distinct. The Ω = 0± components, as expected, are nearly degenerate.
Variations of the energy splittings between different spin-orbit components of the 3 3Π state with respect to internuclear distance. The splittings are largest near ∼5.5 Å, corresponding to the bottom of the well.
PA spectra indicating the overlapping 3(0+) and 5(1) bands, with the REMPI detection laser frequency fixed at (a) 16610.35 cm−1, (b) 16624.76 cm−1, and (c) 16644.01 cm−1. The three PA spectra confirm the reproducibility of the spectral features. The 5(1), J′ = 2 line is from v′ = 17 and correlates to the short-range 2 1Π state. 7 This is the excited state that produces a 3Σ+ state molecules with v″ = 14–25, and is marked by an asterisk. The dashed vertical bar for J′ = 4 indicates the predicted position of this line relative to J′ = 2–3.
REMPI spectra with the PA laser fixed on the 5(1), v′ = 17, J′ = 2 level, at 12535.13 cm−1. The strong signals indicated by vertical bars correspond to atomic Rb nd ← 5s two-photon transitions for which Rb+ leaks into the KRb+ detection channel. A variety of transitions corresponding to 3 3ΠΩ, v′ ← a 3Σ+, v″ bands were observed, where v′ = 2–12 and v″ = 14–25. The red double-headed arrow indicates the region shown in Figure 7 .
An expanded portion (indicated by the double headed arrow) of the REMPI spectrum shown in Figure 6 . Panel (a) indicates 3 3Π0, v′ ← a 3Σ+, v″ transitions; (b) indicates 3 3Π1, v′ ← a 3Σ+, v″ transitions; and (c) indicates 3 3Π2, v′ ← a 3Σ+, v″ transitions. The numbers above the top of the horizontal bars indicate v″, whereas the numbers on the side of the vertical bars indicate v′. A restricted set of v″ transitions is shown to avoid congestion. The numbers at the top axis indicate atomic Rb two-photon transitions.
Comparison of theoretical and experimental values of the vibrational spacings, ΔG v + 1/2 (cm−1) for the levels of 3 3ΠΩ states, where (a) shows the 3 3Π0 state, (b) the 3 3Π1 state, and (c) the 3 3Π2 state. The theoretical values are obtained using LEVEL 22 with the modified potentials reported in Sec. III . The experimental values are obtained from the present work. The insets show an expanded view of the regions indicated by the rectangles (orange).
The solid (black) double minimum potential curve shows the 3 3Π1 state, shifted down by 139 cm−1 (indicated by the double headed arrow). The original approximate potential curve is indicated by the dashed (red) line. The solid horizontal lines indicate the vibrational level positions of the 3 3Π1 state for which v′ = 0 and 1 levels are calculated, but not experimentally observed. The other solid (blue) potential curve is the 4 3Σ+ state. The horizontal dashed lines indicate the vibrational levels of the 4 3Σ+ state that have been experimentally observed. 10 Note the near-degeneracy of the v′ = 6 and 8 levels of the 3 3Π1 state with the v′ = 15 and 16 levels of the 4 3Σ+ state, respectively.
The FCFs for 3 3Π1, v′ =0–11 ← a 3Σ+, v″ = 20 and 24, calculated using LEVEL. 22
The vibrational wavefunctions of the 3 3Π1 double-minimum state for v′ = 0–11, J′ = 0, calculated using LEVEL. 22
Redrawing of the PA spectra shown in Figure 5(b) with additional dotted lines indicating the predicted positions of 39K hyperfine ghosts of the 3(0+), v′ = 118 rotational band. The dashed vertical bar for J′ = 4 indicates the predicted position of this line relative to J′ = 2–3.
Comparison of the REMPI spectra with PA fixed at 5(1), J′ = 2 (black, narrower width) and at 3(0+), J′ = 1 (red, thicker width). The “nd” notations indicate the atomic two-photon transitions that leaked into the molecular channel. These lines serve as precise internal references for calibration of each spectrum.
Contributions of various J′s (of 3 3ΠΩ states) to the overall lineshape of the REMPI signals.
Comparison of experimental and theoretical term energies values of the vibrational levels v′ = 0–12 of the state. We also compare the theoretical vibrational term energies of the and states, for the vibrational levels v′ = 0–12. The term energies are reported with respect to the K(4s 1/2) + Rb(5s 1/2) asymptote and are in units of cm−1. The “†” indicates uncertain vibrational assignment due to poor signal-to-noise ratios.
Comparison of experimental and theoretical term energies of the vibrational levels v′ = 0–11 of the 3 3Π1 state. The term energies are reported with respect to the K(4s 1/2) + Rb(5s 1/2) asymptote and are in units of cm−1.
Comparison of experimental and ab initio term energies of the vibrational levels v′ = 0–11 of the 3 3Π2 double minimum state. The term energies are reported with respect to the K(4s 1/2) + Rb(5s 1/2) asymptote and are in units of cm−1. The “†” indicates uncertain vibrational assignment due to poor signal-to-noise ratios.
Article metrics loading...
Full text loading...