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  • Electronic Resource  (21)
  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 3342-3343 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The hyperfine structure of the 1 3Δg Rydberg state of Na2 has been studied by sub-Doppler CW perturbation facilitated optical–optical double resonance (PFOODR) spectroscopy via A 1Σu+∼b 3Πu mixed intermediate levels.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 43-50 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Using resolved fluorescence from a 1Σ+g Rydberg state to the A 1Σ+u state of K2, we have observed the lowest vibrational levels (v'≤12) of the A 1Σ+u state. Levels v'=21 to 62 (well beyond the previously known v'=12 to 18 region) were observed using the polarization optical–optical double resonance technique. Molecular constants and a Rydberg–Klein–Rees (RKR) potential energy curve based on these constants are given. Franck–Condon factors for the K2, A 1∑+u–X 1∑+g system based on this new A 1Σ+u potential are also given.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 8835-8841 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present here the best qualitative and quantitative illustration to date of the perturbation "gateway'' effect in collision-induced transitions between two mutually perturbing electronic states. The gateway effect, as described by Gelbart and Freed [Chem. Phys. Lett. 18, 470 (1973)], is a suggestion that all collision-induced transfer of population between two electronic states proceeds through a small number of isolated-molecule eigenstates which are of mixed electronic character, the "gateway levels,'' and that the rates for such gateway-mediated processes are related to the mixing fractions in the gateway levels. The gateway levels here are the Na2 A 1Σu+ v'=26∼b 3Π2u v'=28 J'=16e,a-symmetry levels which are significantly mixed owing to an extremely small spin–orbit perturbation matrix element (the neighboring J'=15 and 17e,s-symmetry levels are essentially free of mixing). A cw optical–optical double resonance (OODR) scheme is used to PUMP a single parent level and PROBE single daughter and granddaughter levels.The oscillator strengths for the PUMP and PROBE transitions are derived, respectively, from the A 1Σu+←X 1Σg+ (26,4) band and the 2 3Π2g←b 3Π2u (28,28) subband. The qualitative observation of the gateway effect is that whenever an a-symmetry A 1Σu+ v'=26 parent level is selected, b 3Π2u v'=28 daughter and granddaughter levels are observably populated, but when an s-symmetry A 1Σu+ v'=26 parent is selected, essentially no population is detected in b 3Π2u v'=28 daughter and granddaughter levels (i.e., no perturbation, no interelectronic state transfer). The quantitative observation of the gateway effect is that when a J'=12 (or 14)e,a parent is selected, the most efficiently populated rotational levels of the other electronic state are granddaughter levels centered about the J'=16e,a gateway daughter level rather than about the J' value of (or minimum energy gap relative to) the parent level.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 7783-7783 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 7211-7219 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Na2 b 3Πu state has been studied by the continuous wave (cw) all-optical triple resonance (AOTR) technique. The AOTR technique used here corresponds to a perturbation-facilitated optical–optical double resonance (PFOODR) excitation through A 1Σu+∼b 3Πu mixed intermediate levels from the ground state to the 2 3Πg state and stimulated emission pumping (SEP) of the 2 3Πg→b 3Πu transition. This sub-Doppler high-resolution PFOODR-SEP technique has allowed us to reach many b 3Πu levels (Ω=0, 1, 2, perturbed and unperturbed, including low v below the A 1Σu+ potential minimum and higher vibrational levels up to v=57). Based on these new high resolution data and previous results from high resolution spectroscopy, we have determined a new set of deperturbed molecular constants from the b 3Πu state up to v=57, the corresponding RKR potential energy curve and the A 1Σu+∼b 3Πu spin–orbit interaction constants. This represents an example of a powerful and general technique for observing a "dark'' (e.g., triplet) perturbing state when only the "bright'' (e.g., singlet) perturbed state is well known from single photon spectroscopy.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 8452-8463 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rydberg states of the potassium dimer in the 28 430–29 080 cm−1 and 30 030–30 500 cm−1 regions above the ground state X1Σ+g minimum have been studied using the perturbation facilitated optical–optical double resonance technique (PFOODR). Energy levels in these energy regions have been assigned to both triplet and singlet gerade states based on excitation pattern information as well as intensity considerations. Resolved fluorescence from a mixed triplet–singlet 43Πg ∼1Πg upper state to the ground triplet state a 3Σ+u has been used to construct a potential energy curve for the a 3Σ+u state which is in excellent agreement with recent theoretical results. Since this electronic state and the ground singlet state X1Σ+g share the same dissociation limit, we have determined the dissociation energy for the potassium dimer to be De=4450±2 cm−1.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 8413-8418 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The changes in the hyperfine quantum number (F') that accompany collision-induced ΔJ, ΔΩ, and Δ(e/f-parity) transitions in the Na2 b 3Πu-state have been studied by sub-Doppler, cw, perturbation-facilitated optical–optical double resonance (PFOODR) spectroscopy. The Na2 is contained in a heat pipe oven at ∼1 Torr and the primary collision partner is Na(3s 2S). The PUMP laser selectively excites a single b 3Π0u v'=12, J'=43e, s or 44e, a rotational level, the parent level. All F' hyperfine components of the parent J' level are directly populated by the PUMP laser, but with different velocity projections relative to the laser propagation direction. Thus each parent hf component is labeled by its longitudinal velocity. As the PROBE laser is scanned through various 2 3ΠΩg v=2, J←b 3ΠΩ'u v'=12, J' transitions, sub-Doppler hyperfine structure can be resolved on each parent and daughter rotational line in the PFOODR fluorescence excitation spectrum. The collisional propensity rule ΔF=ΔJ is obeyed for (s, a permutation symmetry conserving) ΔJ'=0, ΔΩ'=0, +1, and +2 and ΔJ'=±1, ±2, ΔΩ'=0 collision-induced transitions. No systematic exploration of the parent-J', Ω' dependence of the ΔF propensity was undertaken; in particular, the present study was restricted to the high-J limit where the Na2/Na collisions are not sudden relative to the rotational (half) period and where J(very-much-greater-than)I. The ΔF=ΔJ hyperfine propensity rule observed for high-J levels of the Na2 b 3Πu state is consistent with previous theoretical predictions of a ΔF=0 propensity for collision-induced ΔJ=0 transitions between Λ-doublet components of the OH X 2Π state and a ΔF=ΔJ propensity for collision-induced transitions between CaBr X 2Σ+ rotational levels.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 6192-6199 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The hyperfine structure of the b 3Πu, 2 3Πg, and 3 3Πg states of 7Li2 has been studied by continuous wave perturbation facilitated optical–optical double resonance fluorescence excitation spectroscopy. The b 3Πu state has case bβJ coupling scheme. The hyperfine splittings of the two perturbed b 3Πu v=19, N=10, J=11e, s, F1 and v=19, N=5, J=4e, a, F3 levels were resolved and hyperfine constants determined to be +9.90 MHz and −20.94 MHz, respectively. Fermi contact is the main source of the hyperfine interaction and bF(b 3Πu)=+107 MHz has been obtained. The coupling schemes of different 2 3Πg levels are different: N=4, 6 levels observed from the b 3Πu v′=19, N′=5, J′=4e, a, F3 intermediate level and the N=10 levels observed via the b 3Πu v′=19, N′=10, J′=11e, s, F1 intermediate level have case bβJ coupling; the N=5 levels observed via the b 3Πu v′=19, N′=5, J′=4e, a, F3 intermediate level and the N=9, 11 levels observed from the b 3Πu v′=19, N′=10, J′=11e, s, F1 intermediate level are closer to case bβS coupling. Hyperfine constants have been calculated and the Fermi contact constant, bF(2 3Πg)=60 MHz is obtained. The 3 3Πg state is a Rydberg state and has case bβS coupling with bF(3 3Πg)≈100 MHz. © 1996 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 3024-3031 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper reports the experimental observation of the 2 3Σ+g, 3 3Σ+g, and 4 3Σ+g states of 7Li2 by cw perturbation facilitated optical–optical double resonance spectroscopy. Molecular constants and RKR potential curves have been obtained. Our experimental Te and Re for the 2 3Σ+g state are 27 297.45(16) cm−1 and 3.0797(18) A(ring), respectively, and for the 3 3Σ+g state are 31 043.93(53) cm−1 and 3.0378(19) A(ring), respectively. The above values are in very good agreement with theoretical calculations. Hyperfine splitting for both states has been resolved. Both states follow Hund's case (bβS) hyperfine coupling scheme. The experimental Fermi contact parameter, bF, is approximately 96±2 MHz for the 2 3Σ+g state and 95.6±3 MHz for the 3 3Σ+g state. These values are in good agreement with the previously obtained value 98.6±4 MHz [Li et al., J. Chem. Phys. 96, 3342 (1992)]. One level of the 4 3Σ+g state has been observed and its hyperfine structure has been resolved and characterized with Hund's coupling case (bβS). © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 3581-3587 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper reports the first experimental observation of the doubly excited valence (2p+2p)3Σ−g state of 7Li2. We used cw perturbation-facilitated optical–optical double resonance (PFOODR) fluorescence excitation and resolved fluorescence spectroscopic techniques. All the observed levels have been detected through perturbations by the 2 3Πg state. The deperturbed primary molecular constants of this 1 3Σ−g state are Te=34 045.354(43) cm−1, ωe=216.820(37) cm−1, Be=0.673 69(47) cm−1, Re=2.670 81(94) A(ring), and De=4279.306(43) cm−1. The equilibrium internuclear distance of the 1 3Σ−g state is smaller than that of the X 1Σ+g ground state.
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