Showing papers by "Richard J. Saykally published in 1986"
TL;DR: In this paper, a very sensitive laser technique was used for measuring the vibrational motions in van der Waals bonds and was used to detect the lowest perpendicular bending vibration in ArHCl near 35 cm−1 with signal-to-noise ratios ≥ 104 and with resolution of nuclear hyperfine structure.
Abstract: We report the development of a very sensitive laser technique for measuring the vibrational motions in van der Waals bonds. This new technique has been used to detect the lowest perpendicular bending vibration in ArHCl near 35 cm−1 with signal‐to‐noise ratios ≥104 and with resolution of nuclear hyperfine structure. A total of 80 Stark‐hyperfine components of the R(0), Q(1), Q(2), rotational lines have been measured with a precision of ≤1 MHz and analyzed by least squares techniques to obtain precise values for the vibrational band origin [ν0=1018 731.20(31) MHz], the dipole moment [μ’=0.260 26(11) D], the effective rotational constant [(B’+C’)/2=1696.70(22) MHz], the l‐type doubling constant [ql =−50.90(35) MHz], and the 35Cl quadrupole coupling constants [eqQ’aa=−6.5(4.1) MHz, eqQ’bb−eqQ’ cc=−74.4(2.2) MHz] in the excited perpendicular (l=±1) bending state. Interpretation of these constants indicates a strongly bent average geometry (θ>51°) for the excited state. These measurements strongly support the r...
84 citations
TL;DR: In this paper, the authors reported the measurement of new high-J transitions (up to J=41) in the fundamental N-H stretch band and of the 1110-0110 bending hot band by velocity modulation infrared laser spectroscopy.
Abstract: We report the measurement of new high‐J transitions (up to J=41) in the fundamental N–H stretch band and of the 1110–0110 bending hot band by velocity modulation infrared laser spectroscopy. These data were combined with measurements of the 100, 0110, and 001 fundamentals of both HNN+ and DNN+, and of the 1110–0110 hot band of DNN+, and of microwave ground state rotational transitions, made by several groups, in a simultaneous weighted least‐squares analysis; from this analysis, the equilibrium structure of protonated nitrogen was determined to be: rNH =1.033 59(43) A, rNN =1.092 766(92) A. Several vibration–rotation and anharmonicity constants were determined; comparisons with high level ab initio calculations are presented.
74 citations
TL;DR: In this article, the results of laser magnetic resonance measurements performed on the ground CII state of singly consumed atomic carbon (C_II) were presented, and the 2^P_(3/2) ← ^2P_(1/2)-fine-structure intervals of both C^+ and C^+) were determined with a precision of approximately 1 ppm and the g_J factors to approximately one part in 10^4.
Abstract: We present the results of laser magnetic resonance measurements performed on the ground ^2P state of singly
ionized atomic carbon (C_II). The 2^P_(3/2) ← ^2P_(1/2) fine-structure intervals of both ^(12)C^+ and ^(13)C^+ have been determined with a precision of approximately 1 ppm, and the g_J factors to approximately one part in 10^4.
Specifically, we find that g_(J=(1/2)) = 0.66576(11) and g_(J=(3/2)) = 1.33412(11), while for ^(12)C^+ ΔE_0(^2P_(3/2) ← ^2P_(1/2))= 1900536.9(1.3) MHz, with ΔE_0(^2P_(3/2) ← ^2P_(1/2)) = 1900545.8(2.1) and ΔE(^2P(3/2) ← ^2P_(1/2), F = 2 ← 1) = 1900466.1(2.3) MHz in ^(13)C^+. The highly precise values of the ^(12)C_II and ^(13)C_II fine-structure intervals verify the already secure far-infrared astronomical identification of C^+ and should allow the interstellar (^(12)C / ^(13)C) ratio to
be unambiguously determined in a number of environments.
62 citations
TL;DR: In this article, the fundamental vibration-rotation bands of 16OH− and 18OH− near 3550 cm−1 were measured with a color center laser and analyzed with a least squares fit yielding vibration−rotation constants through sextic distortion terms.
Abstract: We report the measurement and analysis of the fundamental vibration–rotation bands of 16OH− and 18OH− near 3550 cm−1 by velocity modulation spectroscopy with a color center laser. These bands were analyzed with a least squares fit yielding vibration–rotation constants through sextic distortion terms. From the band origins of the two isotopes, harmonic frequencies and anharmonicities were calculated and a dissociation energy was estimated assuming a Morse potential. Comparisons with high level ab initio calculations are presented. The OH− concentration is found to be dramatically dependent on the presence of metal sputtered on the discharge cell wall.
60 citations
TL;DR: In this article, the axial components of both the anisotropic and rotational g tensors are compared with their calculated values using the Curl relationship and an r0 structure was determined and is in good agreement with several ab initio results.
Abstract: Nine rotational transitions of v=0 X 2B1 H2O+ have been measured by laser magnetic resonance. Optical combination differences have been combined with the LMR data in a weighted least‐squares analysis using a Watson S‐reduced rotational‐fine structure Hamiltonian. Twenty‐four molecular constants were simultaneously determined, including three hyperfine parameters and the axial components of both the anisotropic and rotational g tensors. The anisotropic g tensors are compared with their calculated values using the Curl relationship. An r0 structure was determined and is in good agreement with several ab initio results.
58 citations
TL;DR: In this article, the spectrum of C35Cl+ and C37Cl+ was fitted to a sixth order Dunham expansion to yield an accurate mapping of the Born-Oppenheimer potential function of CCl+.
Abstract: Over 70 transitions among the lowest six vibrational states of C35Cl+ and C37Cl+ have been measured between 1070–1210 cm^−1. The spectrum has been fitted to a sixth order Dunham expansion to yield an accurate mapping of the Born–Oppenheimer potential function of CCl+. The spectroscopic constants obtained are ωe = 1177.7196(8) cm^−1, ωexe = 6.6475(3) cm^−1, and Be = 0.797 940(3) cm^−1. The rotational constants for both CCl+ isotopes reported here show the results of the previous electronic emission studies to be incorrect. A fit of the data to a Morse function yields a dissociation energy D of 52 828(50) cm^−1. The rotational temperature has been determined as 540 K±30%. The increase in the effective vibrational temperature with vibrational excitation indicates that CCl+ is formed with high internal energy.
44 citations
TL;DR: In this paper, the vibration rotation spectrum of the amide anion (NH−2 ) has been measured in the 3 μm region by velocity modulation laser spectroscopy, and the ν1 and ν3 bands have been simultaneously fit to a Watson S reduced Hamiltonian; the band origins are (in cm−1) 3121.9306(61) and 3190.291(14), respectively.
Abstract: The vibration–rotation spectrum of the amide anion (NH−2 ) has been measured in the 3 μm region by velocity modulation laser spectroscopy. The ν1 and ν3 bands have been simultaneously fit to a Watson S reduced Hamiltonian; the band origins are (in cm−1) 3121.9306(61) and 3190.291(14), respectively. The r0 structure has been determined: rNH=1.0367(154), θHNH=102.0(3.3). Under appropriate discharge conditions, NH−2 concentrations near 4×1011 molecules/cm3 can be produced in cells with metal‐coated walls. Comparisons with condensed phase measurements and ab initio calculations are presented.
41 citations
TL;DR: The lowest six vibrational hot bands of CF + have been measured in a helium/C 2 F 6 discharge by velocity modulation laser spectroscopy as discussed by the authors, yielding the parameters: ω e = 17926654(18) cm −1 B e = 17204176(75)cm −1, Y 20, = −1322968(54) cm−1, and D 0 = 62086(30)cm−1
40 citations
31 citations
TL;DR: In this paper, a Born-Oppenheimer equilibrium geometry was employed to calculate the ground state molecular constants, including the three g factors, for the spin-rotation interaction in the X 3 Σ− vibronic ground states of OH+ and OD+ using laser magnetic resonance spectroscopy.
Abstract: Far IR rotational transitions between the four lowest rotational levels in the X 3Σ− vibronic ground states of OH+ and OD+ have been observed by laser magnetic resonance spectroscopy. Ground state molecular constants, including the three g factors, have been determined and employed in the calculation of a Born–Oppenheimer equilibrium geometry. The centrifugal distortion of the spin‐rotation interaction is found to have a significant effect on the determination of other molecular constants. Hyperfine splittings have been resolved and analyzed for OH+, but could not be observed in OD+ spectra with a 6 MHz collision‐broadened linewidth.
31 citations
TL;DR: In this article, the fine-structure intervals in the 3P ground state of neutral atomic C-12 and C-13 as obtained from laser magnetic resonance spectroscopy were investigated.
Abstract: Accurate values are presented for the fine-structure intervals in the 3P ground state of neutral atomic C-12 and C-13 as obtained from laser magnetic resonance spectroscopy. The rigorous analysis of C-13 hyperfine structure, the measurement of resonant fields for C-12 transitions at several additional far-infrared laser frequencies, and the increased precision of the C-12 measurements, permit significant improvement in the evaluation of these energies relative to earlier work. These results will expedite the direct and precise measurement of these transitions in interstellar sources and should assist in the determination of the interstellar C-12/C-13 abundance ratio.
TL;DR: In this article, a self-consistent field and configuration interaction theory was used to predict the nuclear quadrupole moment of H2CN+ and HCN, which is one order of magnitude less than in HCN and provides an explanation for the experimental fact that the fine structure of the microwave spectrum of HCN has not been resolved.
Abstract: Nitrogen 14 quadrupole coupling constants for H2CN+ and HCN are predicted via ab initio self‐consistent‐field and configuration interaction theory. Effects of electron correlation, basis set completeness, and geometrical structure on the predicted electric field gradients are analyzed. The quadrupole coupling constant obtained for H2CN+ is one order of magnitude less than in HCN, providing an explanation for the experimental fact that the fine structure of the microwave spectrum of H2CN+ has not been resolved. This research also allows a reliable prediction of the nuclear quadrupole moment of 14N, namely Q(14N)=2.00×10−26 cm2.
TL;DR: In this article, the hyperfine constants and gJ factors have been evaluated for both isotopes and a complete description of hyperfine and Zeeman Hamiltonian matrix elements for atomic fine structure transitions is given in an LS coupled basis set.
Abstract: Far‐infrared laser magnetic resonance spectroscopy has been used to measure the J=2←1 fine structure intervals in the 3P ground states of singly ionized 14N and 15N atoms. In 14N(II) this separation is 2459.3703(14) GHz, and in 15N(II) it is 2459.3816(19) GHz. The hyperfine constants and gJ factors have been evaluated for both isotopes. Zero field energies for the hyperfine components of the J=2←1 transition in both isotopes are given in an effort to facilitate their observation in interstellar sources. A complete description of the hyperfine and Zeeman Hamiltonian matrix elements for atomic fine structure transitions is given in an LS coupled basis set.
TL;DR: In this article, the L.M.R. spectra were analyzed in terms of an effective hamiltonian to yield an improved set of molecular parameters, and three rotational transitions of CO in the 1 and 2 spin components of the metastable (τ ∼ 7 ms) a 3 ǫ state were measured by far infrared laser magnetic resonance spectroscopy of a positive column discharge.
Abstract: Three rotational transitions of CO in the Ω = 1 and Ω = 2 spin components of the metastable (τ ∼ 7 ms) a 3п state have been measured by far infrared laser magnetic resonance spectroscopy of a positive column discharge. The L.M.R. spectra were analysed in terms of an effective hamiltonian to yield an improved set of molecular parameters.
Proceedings Article•
09 Jun 1986TL;DR: In this article, velocity modulation detection employed with color center and diode lasers was used to study IR spectra of negative (OH−, NH 2 −) and positive (H3O+, NH 4 +, CF+, HNN+) ions.
Abstract: Velocity modulation detection employed with color center and diode lasers was used to study IR spectra of negative (OH−, NH 2 −) and positive (H3O+, NH 4 +, CF+, HNN+) ions, Far-IR laser techniques have been used to study OH+, H2O+, and ArH+. Details will be discussed.
Journal Article•
TL;DR: In this article, velocity modulation detection employed with color center and diode lasers was used to study IR spectra of negative (OH−, NH 2 −) and positive (H3O+, NH 4 +, CF+, HNN+) ions.
Abstract: Velocity modulation detection employed with color center and diode lasers was used to study IR spectra of negative (OH−, NH 2 −) and positive (H3O+, NH 4 +, CF+, HNN+) ions, Far-IR laser techniques have been used to study OH+, H2O+, and ArH+. Details will be discussed.