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  • Digitale Medien  (21)
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  • Digitale Medien  (21)
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  • 1
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 912-918 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: CW optical–optical double resonance has been employed to study the upper portion of the G 1Πg state of 7Li2. The use of fluorescence and ion detection enabled the observation of vibrational levels ranging from v=20 to 48 and rotational levels ranging from J=1 to 25. For optical–optical double resonance experiments the Franck–Condon factors between these levels and useful A 1Σu+ state levels (levels that can be reached from the thermally populated levels of the ground state) were exceedingly small. The sensitive ionization detection made possible observation of this upper, anharmonic region of the potential. From the data a Rydberg–Klein–Rees potential curve was constructed which represents over 99% of the potential well depth. A C5 coefficient has been calculated and represents the first experimental determination of a long range coefficient for a doubly excited state in diatomic lithium.© 1998 American Institute of Physics.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 6646-6652 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The 4 3Σ+g, 3 3Πg, and 2 3Δg states of K2 have been studied by perturbation facilitated optical–optical double resonance spectroscopy for the first time. Molecular constants of those states are derived and compared with theoretical calculations. Varying the trial vibrational quantum numbers of these upper states, absolute vibrational quantum number assignments are obtained by comparison between the observed resolved fluorescence intensities and the calculated Franck–Condon factors. The Rydberg–Klein–Rees potential curves are constructed and compared with theoretical calculations. Finally, the observation of the lowest "dark'' vibrational levels of the b 3Πu state by resolved fluorescence from the 2 3Δg state confirmed the absolute vibrational numbering of this state and allowed refinement of the b 3Πu molecular constants. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 3581-3587 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 9859-9863 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: State-to-state collision energy transfer in the 2 3Πg, 3 3Πg, 3 3Σ+g, 1 3Σ−g, and 1 3Δg states and from singlet to triplet states of 7Li2 has been studied experimentally by continuous wave optical–optical double resonance (OODR) resolved fluorescence spectroscopy. Propensity rules of collision-induced transitions within a triplet state have been observed. When a rovibrational (v,J) level of the F 1Σ+g or G 1Πg state was excited by OODR transition, fluorescence from high-lying triplet gerade states to the a 3Σ+u and/or b 3Πu states was always observed. This indicates that population can transfer from F 1Σ+g and G 1Πg states to triplet states by collision. Irrespective of the J of the initially excited singlet level, the most intense fluorescence from the triplet state will occur at the N or J corresponding to that of the F 1Σ+g (and/or G 1Πg)∼3Λg mixed levels. Molecular population moves to the mixed levels and then transfers to the triplet state. This clearly indicates that singlet–triplet mixed levels played the role of a gateway, through which the population moves from singlet to triplet states. The gateway levels can be perturbed levels in the same vibrational level of the F 1Σ+g or G 1Πg state, or the perturbed levels in different vibrational levels. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Resolved fluorescence from the K2 43 Σ+g state to the a3 Σ+u state has been measured by the perturbation-facilitated optical–optical double resonance (PFOODR) technique. Data have been fit to an improved set of molecular constants for the a3 Σ+u state. In particular, the new Te value for this state has been determined as 4197.935±0.047 cm−1, nearly 1.8 cm−1 higher than previously reported. By combining the new results for the a3 Σ+u state and the recent results for the ground X1 Σ+g state [J. Chem. Phys. 103, 3350 (1995)], we report in this paper an improved analysis of long-range dispersion and exchange interactions between two K atoms and of the X1 Σ+g and a3 Σ+u state dissociation energies De of 4450.674±0.072 cm−1 and 252.74±0.12 cm−1, respectively. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 6192-6199 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: 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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  • 7
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 2813-2817 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The A 1Σ+u state of 7Li2 has been studied using all optical triple resonance spectroscopy. Vibrational levels v=27–62 and rotational levels ranging from J=0 to 27 have been observed. This represents a region between previous data from single photon experiments and new data from cold atom photoassociative spectroscopy. Our data was fit to a Dunham expansion and the resulting molecular constants reproduce most observed energies to within 0.050 cm−1. A Rydberg–Klein–Rees potential curve has also been constructed and the calculated eigenvalues are in good agreement with observed energies. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
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  • 8
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 5493-5504 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We have measured the far wing absorption profiles of the MgH2 collision system leading to both the nonreactive formation of Mg* and into two distinct final rotational states of the reaction product MgH (v‘=0, J‘=6, 23). We have observed qualitatively expected behavior including a pronounced red wing in the reactive absorption profile indicating strong reaction probability on the excited attractive potential surfaces. We have also observed novel aspects of the excited state dynamics including reactive vs nonreactive channel competition effects and a strong far blue wing reactive absorption suggesting significant reaction probability even for trajectories on the repulsive surfaces. We have developed a simple theoretical model to semiquantitatively explain our experimental results. This model uses standard quasistatic theory to estimate the absorption probability as a function of detuning between levels of MgH2 and with assumed nonreactive vs reactive branching ratios, accounts for the subsequent evolution on the excited potential surfaces. This theory correctly predicts the overall shapes of the profiles and in general gives reasonable predictions for the relative magnitudes of the wing intensities.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 8413-8418 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
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