Tsuneo Hashi

Excitation and Detection of Coherence between Forbidden Levels in Three-Level Spin System by Multi-Step Processes

The coherent superposition of the states between which magnetic dipole transition is forbidden has been excited and detected by means of a multi-step application of resonant rf pulses in a three-level NMR system. The experiment was carried out on 27 Al nuclei in Al 2 O 3 where the quantization axes of the quadrupole and the magnetic coupling were parallel. Free decay and echo signals associated with the coherence were observed, and transfer of coherence between nonresonant pairs of levels was studied in detail.

Transient Nutations and Spin Echoes Associated with Two-Quantum Transition in Multi-Level NMR System

We report the first observation of transient nutations, spin echoes and stimulated echoes associated with two-quantum transition between levels for which single-quantum transition is forbidden. The experiment was made on a multi-level NMR system, 27 Al in Al 2 O 3 with its c -axis parallel to the static magnetic field H 0 , where level spacings were unequal and no state mixing existed. To detect the coherence between levels with Δ m =2 the technique of transfer of coherence was used. The equation of motion of the spins was simpler than that usually used in a three-level system.

Nuclear Magnetic Resonance of Fe57 in Nickel- and Nickel-Zinc-Ferrites

The nuclear magnetic resonance (NMR) of Fe 57 in Ni- and Ni-Zn-ferrites at zero external field was observed by using a pulsed NMR method. The resonance line-widths were too broad to be detected by the steady-state method. In Ni-ferrite, two resonance lines corresponding to Fe +3 ions at tetrahedral site and at octahedral site were separately observed. At room temperature, the center frequencies of the resonance lines were 67.6 Mc/sec and 72.0 Mc/sec, and their widths were 1.7 Mc/sec and 2.0 Mc/sec, respectively. Temperature dependences were also studied. The effects of substitution of Zn for Ni on NMR of Fe 57 in Ni-ferrite were studied. The NMR signals could be observed up to 30% substitution of Zn at room temperature and up to 50% at liquid air temperature. By substituting Zn for Ni, the resonance line corresponding to octahedral site becomes broader and shifts to the lower frequency side, while that corresponding to tetrahedral site is affected very little. Mossbauer studies were also carried out to ch...

Synchronized quantum beat spectroscopy using periodic impact excitations with CW mode-locked laser pulses

Abstract A novel technique of laser spectroscopy using synchronously accumulated quantum beats produced by periodic impact excitations is demonstrated in an experiment on sodium vapor. Picosecond light pulses (pulse repetition frequency ƒ≈ 128 MHz) from a cw mode-locked dye laser is used for excitation. Quantum beat signals are synchronously accumulated when the sublevel splittings are equal to nf ( n = 0−19 in the present experiment) and detected through the polarization change of a probe team. Splittings between Zeeman and hyperfine sublevels in the ground state 3 2 S 1 2 were detected in a frequency range of 0−2.4 GHz free from the Doppler and lifetime broadening of the optical transition.

Observation of Two-Quantum Rotary Echoes in Multi-Level NMR System

Two-quantum rotary echoes predicted by Bloch like equations for two-quantum transition have been observed in a multi-level NMR system of 27 Al nuclei in Al 2 O 3 . An rf field exactly at resonance to the two-quantum transition ( Δ m =2) was turned on at t =0 and its phase was shifted by 90° at t =τ. The echo at t =2τ was observed by using the technique of transfer of coherence reported previously. Characteristic dependence of the echo width upon inhomogeneity of rf field amplitude was confirmed experimentally.

Spin-locking, spin-locked echo and rotary saturation associated with a two-quantum transition in a multilevel NMR system

Abstract We have observed a two-quantum analog of spin-locking and spin-locked echo, and single and multiple quantum rotary saturation in the two-quantum spin-locked state in a multilevel NMR system, 27 Al in Al 2 O 3 .

Measurements of Chemical-Shift Tensors in KH2PO4 by First-Moment Method

A method is described which allows chemical shifts in solids to be detected to a good accuracy by sharply determining the first moment. The analysis is made by using spin-temperature concepts and it is shown that the chemical-shift tensor can be determined if a single tensor contributes to the spectrum, and the average if more than one tensor contributes. Measurements are made in a single crystal of KH 2 PO 4 . The average tensors obtained are axially symmetric about the c axis with σ // =-25.6 ppm and σ ⊥ =-8.3 ppm relative to C 6 H 12 for 1 H(300 K), and with σ // =-1.1 ppm and σ ⊥ =-16.5 ppm relative to 85% H 3 PO 4 for 31 P(77 K). These values are discussed qualitatively. The 19 F chemical shift in CaF 2 is also obtained, and the result is in good agreement with that of pulse train method.

A Study of Sorbed Water on Cellulose by Pulsed NMR Technique

The state of sorbed water on cellulose has been studied by pulsed NMR technique. From the experimental results of spin-lattice relaxation time ( T 1 ) and spin-spin relaxation time ( T 2 ), observed as a spin echo decay time, following conclusions have been derived. (1) Two phases of the sorbed water are classified; the localized and the mobile. (2) The correlation time (τ N ) derived from T 1 using BPP theory, is consistent with that (τ D ) derived from dielectric measurements. (3) T 1 is by one or two order longer than T 2 in contradiction to BPP theory for extremely narrowing case. As an explanation for this fact, we propose that, when we consider about T 2 , the effects of magnetic nuclei contained in the absorbent must be taken into account, though no theory is given. (4) The average life-time of water molecule sorbed on cellulose in the localized state is estimated to be several hundredths of a second and to decrease with temperature.

Sublevel echoes induced by resonant light pulses: Quantum beat echoes

Abstract We predict and observe a new class of echoes of atomic sublevel coherences induced by two impact excitations with resonant light pulses which may be either coherent or incoherent. The Zeeman-sublevel echoes in 3 2S 1 2 of sodium were observed by using polarization selective detection technique under the excitation condition that the optical T2 (5 × 10-11 s) was much shorter than the pulse width (5 ns). Theoretical analysis also predicts the echoes involving coherence transfer between ground and excited states.

Observation of multiple optical hole burning in ruby

Abstract Direct observation of optical hole burning in ruby is made by using a Stark-field sweeping technique. In addition to the main hole at the laser frequency, new side holes at the shifted frequencies are observed. The origin of the side holes is considered to be due to the population redistribution of resonant ions in the ground state 4 A 2 by spin-spin cross relaxation and that in the excited state Ē( 2 E) by spin-lattice relaxation. Differences from the observation by Szabo and the applicability to high resolution spectroscopy are discussed.