Experimental setup. M is mirror, BS is beam splitter, IF is interference filter, L is lens, and PMT is photomultiplier tube.
PFOODR pump and probe scheme used to study the NaCs 53Π0 and 1(a)3Σ+ states. The thick downward arrow indicates the 53Π0 → 1(a)3Σ+ bound-free emission.
NaCs 53Π0(v, J) → 1(a)3Σ+ bound-free emission spectra for (v, J) = (0, 31), (1, 25), (2, 25), (3, 43), (4, 33), (5, 33), (6, 45), (7, 31), (9, 33), (10, 31), and (14, 31). Only v is used to label the scans in the figure since the bound-free emission depends only weakly on J.
Collisional lines observed using the OODR technique with the pump laser frequency fixed on the 1(b)3Π0(v b , J = 44) ∼ 2(A)1Σ+(v A = 18, J = 44) ← 1(X)1Σ+(v X = 0, J = 43) transition while the probe laser frequency is scanned. The direct probe transitions 53Π0(v = 16, J = 43, 45) ← 1(b)3Π0(v b , J = 44) ∼ 2(A)1Σ+(v A = 18, J = 44) (labeled P(44) and R(44) in the spectrum) extend far off-scale. A series of collisional lines adjacent to each direct line is clearly visible, and it can be seen that rates for collisional population transfer fall monotonically with increasing |ΔJ|.
Schematic diagrams showing the technique for using collisional lines to measure NaCs 53Π0 ro-vibrational level energies relative to known 1(X)1Σ+ level energies. In (a), the pump frequency is scanned while the probe frequency is fixed. Pump laser frequencies corresponding to the observed collisional lines determine intermediate 1(b)3Π0(v b , J) ∼ 2(A)1Σ+(v A , J) level energies relative to known ground state energies. In (b), the probe frequency is scanned while the pump frequency is fixed. Probe frequencies corresponding to the observed collisional lines determine 53Π0(v, J) level energies relative to the 1(b)3Π0(v b , J) ∼ 2(A)1Σ+(v A , J) level energies.
Measured vibrational level spacings ΔG v + 1/2 = G(v + 1) − G(v) for the NaCs 53Π0 state.
IPA and theoretical NaCs 53Π0 potential energy curves.
Differences between experimental NaCs 53Π0 ro-vibrational level energies and those calculated using the program LEVEL 8.0115 with the present 53Π0 IPA potential. Note that this plot includes all measured levels used in the Dunham coefficient and IPA potential fits (blue diamonds), as well as those that were excluded from the fits (red triangles).
NaCs 53Π0(v = 10, J = 31) → 1(a)3Σ+ bound-free spectrum and simulation using the present IPA 53Π0 potential and the Docenko et al. 12 1(a)3Σ+ potential (including the V Wall(R) ∼ R −3 repulsive wall). In the simulation, the transition dipole moment function was taken to be constant with R. The pair of vertical black solid lines represents the range of wavelengths in which bound–bound transitions occur.
Best “global fit” of the NaCs 1(a)3Σ+ state repulsive wall. The repulsive wall obtained in the global fit presented in this work is plotted along with the 1(a)3Σ+ potential of Docenko et al. 12 (including their R −3 extrapolation of the repulsive wall).
NaCs 53Π0 → 1(a)3Σ+ transition dipole moment function. The blue curve represents the best “global fit” of the 53Π0 → 1(a)3Σ+ relative transition dipole moment function from the present work, while the red curve is the theoretical 53Π0 → 1(a)3Σ+ transition dipole moment function of Aymar and Dulieu.111 Since the experimental curve is only a relative transition dipole moment function, it has been normalized (by multiplying the function described by Eqs. (4) and (5) and the parameters listed in Table III by the factor −9.9066) to the theoretical curve in a least squares sense over the range 3.7 Å < R < 6.3 Å.
NaCs 53Π0(v, J) → 1(a)3Σ+ resolved fluorescence spectra (blue) and simulated spectra (red) based on the 1(a)3Σ+ state repulsive wall and 53Π0 → 1(a)3Σ+ relative transition dipole moment function global fit parameters. Comparisons of experimental and simulated resolved fluorescence spectra from additional upper levels can be found in Ref. 104. Each pair of vertical black solid lines represents the range of wavelengths in which bound–bound transitions occur.
Vector coupling diagrams used to determine hyperfine structure in the case a β , b βJ , and c β limits.
Dunham coefficients obtained from fit of NaCs 53Π0(v, J) level energies in the range 0 ⩽ v ⩽ 22 to the Dunham expansion, Eq. (1). All values are in cm−1. The centrifugal distortion term, Y(0, 2), was fixed at the value −7.2 × 10−8 cm−1.
NaCs 53Π0 IPA potential energy curve obtained in this work.
Parameters describing the NaCs 1(a)3Σ+ repulsive wall [Eq. (3)] and the 53Π0 → 1(a)3Σ+ transition dipole moment function [Eqs. (4) and (5)] resulting from the global fit of the 53Π0(v, J) → 1(a)3Σ+ resolved bound-free fluorescence spectra.
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