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  • 1
    Electronic Resource
    Electronic Resource
    Structural and energetic properties of the Br−–C2H2 anion complex from rotationally resolved mid-infrared spectra and ab initio calculations (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 1075-1080 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An infrared vibrational predissociation spectrum of the 79Br−–C2H2 anion complex has been recorded over the 2800–3400 cm−1 range. Bands are observed that correspond to excitation of bound and free C–H stretches of an acetylene molecule engaged in a linear hydrogen bond with Br−. The band associated with the bound C–H stretch displays rotationally resolved substructure. Lower J transitions are absent from the predissociation spectrum, indicating that the upper levels lie below the dissociation threshold. Analysis leads to constants for lower and upper states: v0=2981.28, B″=0.048 84, ΔB=9.3×10−4 cm−1, and a minimum J′=28 for dissociation. The rotational constants correspond to vibrationally averaged separation between Br− and the C2H2 center of mass of 4.11 Å in the ground state and 4.07 Å in the v3 state. A dissociation energy for Br−–C2H2 of 3020±3 cm−1 is estimated from the energy of the lowest dissociating level. The spectroscopically derived data are corroborated by ab initio calculations conducted at the MP2/aug-cc-pVTZ level. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481919
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  • 2
    Electronic Resource
    Electronic Resource
    Infrared spectra of Cl−–(C2H2)n (1≤n≤9) anion clusters: Spectroscopic evidence for solvent shell closure (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 9443-9449 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Mid-infrared vibrational predissociation spectra of mass selected Cl−–(C2H2)n (1≤n≤9) complexes have been recorded in the vicinity of the acetylene ν3 vibrational band (2700–3400 cm−1). For clusters containing up to 6 acetylene ligands, the spectra each feature a single dominant band, shifted to lower frequency from the ν3 C–H stretch band of free acetylene, and are consistent with interior solvation structures, whereby roughly equivalent acetylene molecules are bound end-on to a central chloride anion. Spectra of the n=7, 8, and 9 complexes, display multiple peaks and provide evidence for acetylene molecules situated in a second solvation shell and also for the existence of multiple isomeric forms. Depending on the cluster size, the inner solvation shell contains 6–8 acetylene molecules. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478909
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  • 3
    Electronic Resource
    Electronic Resource
    Mid-infrared spectra of He–HN+2 and He2–HN+2 (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 3876-3885 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Mid-infrared vibrational spectra of He–HN+2 and He2–HN+2 have been recorded by monitoring their photofragmentation in a tandem mass spectrometer. For He–HN+2 three rotationally resolved bands are seen: the fundamental ν1 transition (N–H stretch) at 3158.419±0.009 cm−1, the ν1+νb combination band (N–H stretch plus intermolecular bend) at 3254.671±0.050 cm−1, and the ν1+νs combination band (N–H stretch plus intermolecular stretch) at 3321.466±0.050 cm−1. The spectroscopic data facilitate the development of approximate one-dimensional radial intermolecular potentials relevant to the collinear bonding of He to HN+2 in its (000) and (100) vibrational states. These consist of a short range potential derived from an RKR inversion of the spectroscopic data, together with a long range polarization potential generated by considering the interaction between the He atom and a set of multipoles distributed on the HN+2 nuclei. The following estimates for binding energies are obtained: D0″=378 cm−1 [He+HN+2(000)], and D0′=431 cm−1 [He+HN+2(100)]. While the ν1 band of He2–HN+2 is not rotationally resolved, the fact that it is barely shifted from the corresponding band of He–HN+2 suggests that the trimer possesses a structure in which one of the He atoms occupies a linear proton-bound position forming a He–HN+2 core, to which a second less strongly bound He is attached. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471244
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  • 4
    Electronic Resource
    Electronic Resource
    The infrared spectrum of the H2–HCO+ complex (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 5152-5164 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A combined experimental and theoretical study of the structural properties of the H2–HCO+ ion-neutral complex has been undertaken. Infrared vibrational predissociation spectra of mass selected H2–HCO+ complexes in the 2500–4200 cm−1 range display several vibrational bands, the most intense arising from excitation of the C–H and H2 stretch vibrations. The latter exhibits resolved rotational structure, being composed of Σ–Σ and Π–Π subbands as expected for a parallel transition of complex with a T-shaped minimum energy geometry. The determined ground state molecular constants are in good agreement with ones obtained by ab initio calculations conducted at the QCISD(T)/6–311G(2df,2pd) level. The complex is composed of largely undistorted H2 and HCO+ subunits, has a T-shaped minimum energy geometry with an H2...HCO+ intermolecular bondlength of approximately 1.75 A(ring). Broadening of the higher J lines in the P and R branches of the Π–Π subband is proposed to be due to asymmetry type doubling, the magnitude of which is consistent with the calculated barrier to H2 internal rotation. The lower J lines in the Σ–Σ and Π–Π subbands have widths of 0.06 cm−1, around three times larger than the laser bandwidth, corresponding to a decay time of ≈90 ps for the upper level. The absence of discernible rotational structure in the ν2 band suggests that it has predissociation lifetime of less than 1 ps. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469240
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  • 5
    Electronic Resource
    Electronic Resource
    The infrared spectrum of the N2H+–He ion-neutral complex (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 5570-5571 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rotationally resolved, vibrational predissociation spectra of the HN+2–He complex have been recorded in the region of the N–H stretch (3100–3200 cm−1). The complex appears to be linear. Fitting of the measured lines to the pseudodiatomic expression ν=ν0+(B'ν+B‘ν)m +(B'ν−B‘ν–D'ν+D'ν) m2−2(D'ν+D‘ν)m3 −(D'ν−D‘ν)m4 yields the following constants: ν0=3158.419±0.009 cm−1, B‘=0.3517±0.0005 cm−1, D‘=(5.8±0.5)×106 cm−1, B'=0.3579 ±0.0005 cm−1, D'=(3.9±0.6)×106 cm−1. The data support a proton bound He–HNN+ structure, with a 1.72 A(ring) vibrationally averaged intermolecular bondlength, and an approximate intermolecular stretching frequency of 150 cm−1. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469286
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  • 6
    Electronic Resource
    Electronic Resource
    The 35Cl−–H2 and 35Cl−–D2 anion complexes: Infrared spectra and radial intermolecular potentials (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 824-832 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rotationally resolved mid-infrared spectra of the 35Cl−–H2 and 35Cl−–D2 anion complexes are measured in the regions associated with the H2 and D2 stretch vibrations. The 35Cl−–H2 spectrum contains a single Σ–Σ transition assigned to the more abundant ortho H2 containing species. The corresponding 35Cl−–D2 spectrum consists of two overlapping Σ–Σ transitions whose origins are separated by 0.24 cm−1, and which are due to absorptions by complexes containing para and ortho D2. The spectra are consistent with linear equilibrium structures for Cl−–H2 and Cl−–D2, although zero-point bending vibrational excursions are expected to be substantial. Ground state vibrationally averaged intermolecular separations between Cl− and the diatomic center-of-mass are deduced to be 3.195±0.003 Å (35Cl−–H2) and 3.159±0.002 Å (35Cl−–D2). Vibrational excitation of the diatomic core profoundly affects the intermolecular interaction and leads to contractions of 0.118 Å (35Cl−–H2) and 0.078 Å (35Cl−–D2) in the vibrationally averaged intermolecular separations. Effective one-dimensional radial potential energy curves are developed. Their form near the equilibrium separation is determined by Rydberg–Klein–Rees inversion of the spectroscopic data, and at longer ranges by averaging the dominant long range electrostatic and induction potentials over the angular motion of the atom–diatomic system. On the basis of these potentials the dissociation energies for 35Cl−–H2(o), 35Cl−–D2(p), and 35Cl−–D2(o) are estimated as 488, 499, and 559 cm−1. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1378039
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  • 7
    Electronic Resource
    Electronic Resource
    Br−-H2 and I−-H2 anion complexes: Infrared spectra and radial intermolecular potential energy curves (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 117 (2002), S. 3256-3262 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Midinfrared spectra of the 81Br−-H2 and I−-H2 anion complexes are measured in the H-H stretch region by monitoring the production of halide anion photofragments. The spectra, which are assigned to complexes containing ortho H2, exhibit rotationally resolved ∑-∑ bands whose origins are redshifted from the molecular hydrogen Q1(1) transition by 110.8 cm−1 (Br−-H2) and 74.1 cm−1 (I−-H2). The complexes are deduced to possess linear equilibrium structures, with vibrationally averaged intermolecular separations between the halide anion and H2 center of mass of 3.461 Å (Br−-H2) and 3.851 Å (I−-H2). Vibrational excitation of the H2 subunit causes the intermolecular bond to stiffen and contract by 0.115 Å (Br−-H2) and 0.112 Å (I−-H2). Rydberg–Klein–Rees inversion of the spectroscopic data is used to generate effective radial potential energy curves near the potential minimum that are joined to long-range potential energy curves describing the interaction between an H2 molecule and a point negative charge. From these curves the dissociation energies of Br−-H2 and I−-H2 with respect to isolated H2 (j=1) and halide fragments are estimated as 365 and 253 cm−1, respectively. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1486435
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  • 8
    Electronic Resource
    Electronic Resource
    Rotationally resolved infrared spectrum of the Br−−D2 anion complex (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 6394-6400 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The midinfrared spectrum of the 79Br−−D2 anion complex is measured in the D2 stretch region by monitoring the production of Br− photofragments in a tandem mass spectrometer. The rotationally resolved spectrum comprises two overlapping Σ−Σ subbands, red-shifted by (approximate)85 cm−1 from the free D2 vibrational frequency. These subbands are assigned to absorptions by Br−−D2 complexes containing para and ortho forms of the D2 molecule. The Br−−D2 complex is deduced to possess a linear equilibrium geometry, although the zero-point bending excursion is expected to be substantial. The rotational constants are consistent with vibrationally averaged intermolecular separations between the Br− anion and D2 center of mass of 3.414(4) Å for Br−−D2(p) and 3.413(1) Å for Br−−D2(o). The intermolecular bond contracts by 0.076 Å following vibrational excitation of the D2 diatomic molecule. Effective one-dimensional radial potential energy curves are developed through Rydberg–Klein–Rees inversion of the spectroscopic data and consideration of the long-range electrostatic and induction interaction between the D2 molecule and a point charge. On the basis of these potential energy curves the binding energies of Br−−D2(p) and Br−−D2(o) are estimated as 364 and 418 cm−1, respectively. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1402995
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  • 9
    Electronic Resource
    Electronic Resource
    Photodissociation of (N2)+n clusters (2≤n≤7): Branching ratios for formation of N+2 and N+4, and N+2 fragment vibrational excitation (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 8672-8679 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Dynamical processes accompanying the photofragmentation of (N2)+n clusters (n=3–6) have been investigated. Branching ratios for the formation of N+2 and N+4 photoproducts have been determined at wavelengths spanning the continuous absorption of the chromophore N+4 (630, 532, 396, 315, and 266 nm). In addition, the fraction of N+2 photofragments in excited vibrational states has been found using the monitor gas technique, whereby vibrationally excited N+2 molecules readily exchange charge with Ar buffer gas, and molecules in the υ=0 state do not. For a given sized cluster, as the photon energy increases, there is a trend towards a larger proportion of N+2 compared to N+4 fragments and a mild increase in the fraction of vibrationally excited N+2 fragments. On the other hand, as the size of the primary cluster grows, there is a growth in the proportion of N+4 fragments and a decrease in the fraction of vibrationally excited N+2 fragments. These features of (N2)+n cluster photodissociation are argued to be consistent with primary absorption by a N+4 chromophore core to form energetic N+2 and N2 fragments followed by efficient intracluster recombination, exchange of charge, and exchange of vibrational quanta. The efficiency of these processes for (N2)+3 and (N2)+4 suggest that in these species the N2 ligand(s) is (are) positioned at the end(s) of the linear N+4 ion core.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465591
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  • 10
    Electronic Resource
    Electronic Resource
    The B←X electronic spectrum of N+2–Ne (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 4749-4755 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electronic spectrum of N+2–Ne has been measured in the region corresponding to the B 2∑+u←X 2∑+g origin and 1–0 transitions of N+2. Spectra were obtained by irradiating a mass selected population of N+2–Ne and monitoring the production of N+2 as a function of wavelength. Low temperature N+2–Ne spectra exhibit several well resolved bands. From the shift of the N+2–Ne origin with respect to that of free N+2 it is apparent that the complex dissociation energy D0 is 146.5 cm−1 greater in the B state than the X state. Pronounced changes in the complex's spectrum occur as the effective temperature is increased. The hottest spectra resemble a broadened and truncated N+2 spectrum. The breaking off at the high energy end of the spectrum at elevated temperatures allows us to establish a rough ground-state dissociation energy of 300 cm−1. Other conclusions resulting from this work are that the equilibrium geometry of the N+2–Ne molecule is probably linear in X and B electronic states, that the ΔG1/2 for the low frequency stretch in the B state is 104 cm−1, and that the N–N stretching motion is affected only very weakly by the presence of the Ne atom.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460737
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