The Microwave Spectrum and Molecular Constants of Trifluoromethyl Acetylene

Anderson, Wallace E.; Trambarulo, R.; Sheridan, J.; Gordy, Walter

doi:10.1103/physrev.82.58

Cited by 40 publications

(17 citation statements)

References 5 publications

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“…The simplest case one may study is that of an ellipsoidal sample, where the macroscopic demagnetization field is uniform. The field distribution around randomly placed dipoles is well-known [17] to be a Lorentzian up to a high-energy cutoff defined by E D P α (ξ) = 1 + αM (t) 2…”

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confidence: 99%

Low-Temperature Quantum Relaxation in a System of Magnetic Nanomolecules

1998

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We argue that to explain recent resonant tunneling experiments on crystals of Mn$_{12}$ and Fe$_8$, particularly in the low-T limit, one must invoke dynamic nuclear spin and dipolar interactions. We show the low-$T$, short-time relaxation will then have a $\sqrt{t/\tau}$ form, where $\tau $ depends on the nuclear $T_2$, on the tunneling matrix element $\Delta_{10}$ between the two lowest levels, and on the initial distribution of internal fields in the sample, which depends very strongly on sample shape. The results are directly applicable to the $Fe_8$ system. We also give some results for the long-time relaxation.Comment: 4 pages, 3 PostScript figures, LaTe

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confidence: 99%

Low-Temperature Quantum Relaxation in a System of Magnetic Nanomolecules

1998

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“…We factorize n ± (B || , t) = ρ dipole (B || )n ± (t) where ρ dipole explicitly describes the local field distribution. As an ansatz we use a Gaussian field distribution that is approximately valid for an increasing number of independent, randomly placed spins [10]. Thus…”

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confidence: 99%

Local field dynamics in a resonant quantum tunneling system of magnetic molecules

1998

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We observed non-exponential relaxation for a quantum tunneling molecular magnetic system at very low temperatures and argue that it results from evolving intermolecular dipole fields. At the very beginning of the relaxation, the magnetization follows a square-root time dependence. A simple model is developed for the intermediate time range that is in good agreement with the data over 4 decades in time. Detailed numerical calculations as well as measurements are presented which indicate unusual correlation effects in these systems. PACS. 75.45.+j Macroscopic quantum phenomena in magnetic systems -61.46.+w Clusters, nanoparticles, and nanocrystalline materials -75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects Recent experiments have shown evidence of quantum tunneling of the magnetization in the molecular nanomagnetic systems Fe8 [1] and Mn12ac [2,3]. General theoretical considerations for quantum tunneling of a giant spin through its anisotropy energy barrier have been proposed during the last 10 years [4]. Both Fe8 and Mn12ac can be thought of as an ensemble of identical, iso-oriented nanomagnets of net spin S = 10 with an Ising like anisotropy. Fe8 has the advantage in terms of tunneling measurements in that its anisotropy energy barrier is approximately 24 K compared to 63 K for Mn12ac, and its crystal symmetry affords a sizable transverse anisotropy, both of which greatly enhance tunneling effects [1,4].At low enough temperatures (below 400 mK and approximately 1.8 K, respectively) both systems display a crossover from a thermal activated (over barrier) relaxation to a temperature independent relaxation [1,2] with a remarkable resonant structure of the relaxation time as a function of the external field [1,3]. Below these crossover temperatures and after saturation in a high field, only the m S = +10 state is occupied and the only way relaxation can occur (at the first resonance field B = 0) is by under barrier quantum tunneling from the m S = +10 to the m S = −10 state.Ideally, the relaxation for non interacting, identical (giant) spins would be given by an exponential function M (t) ∝ exp(−t/τ ). However, for Fe8 the data in the low temperature regime is best approximated by a stretched exponential M (t) ∝ exp(−(t/τ stretch ) β ) a

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“…Although the theory was fairly satisfactory for the rotation spectrum of these types of molecules, some of the calculated frequencies by this method were different from the observed frequencies. This formula was extended to the case of higher J values by Gordy et al 9 . The frequency of transition J → J + 1 for molecules belonging to the point group C 3v in singly excited vibrational state v t = 1 is given by the approximate perturbation expression, Eq (3).…”

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confidence: 95%

New Investigation of Millimeter‐Wave Rotational Spectrum of CCl₃CN in Ground, v₇ = 1 and v₈ = 1 States

Motamedi

Zohrevand

2008

Journal of Chemistry

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The millimeter-wave rotational spectra of the ground and excited vibrational states v7=1 and v8=1 of the symmetric top molecule, CCl3CN, have been analyzed again. The B0= 1666.80894(13) MHz, DJ= 0.135023 (23) kHz, DJK= 0.60596 (45) kHz, HJ= -0.0192 (10) mHz, HJK= 1.188 (34) mHz and HKJ= -1.60 (21) mHz have been determined for ground state. The 𝓁 = ±1 series have been assigned and the rotational parameters including B7=1667.96659(25) MHz, (q+t)7=1.58855(94) MHz for v7=1 and B8=1667.08204 (31) MHz, (q+t)8= 1.6141(36) MHz for v8= 1 states were determined accurately.

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The Microwave Spectrum and Molecular Constants of Trifluoromethyl Acetylene

Cited by 40 publications

References 5 publications

Low-Temperature Quantum Relaxation in a System of Magnetic Nanomolecules

Low-Temperature Quantum Relaxation in a System of Magnetic Nanomolecules

Local field dynamics in a resonant quantum tunneling system of magnetic molecules

New Investigation of Millimeter‐Wave Rotational Spectrum of CCl₃CN in Ground, v₇ = 1 and v₈ = 1 States

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The Microwave Spectrum and Molecular Constants of Trifluoromethyl Acetylene

Cited by 40 publications

References 5 publications

Low-Temperature Quantum Relaxation in a System of Magnetic Nanomolecules

Low-Temperature Quantum Relaxation in a System of Magnetic Nanomolecules

Local field dynamics in a resonant quantum tunneling system of magnetic molecules

New Investigation of Millimeter‐Wave Rotational Spectrum of CCl3CN in Ground, v7 = 1 and v8 = 1 States

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Product

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New Investigation of Millimeter‐Wave Rotational Spectrum of CCl₃CN in Ground, v₇ = 1 and v₈ = 1 States