石川 潔

Vibrational levels near the dissociation limit of NaK a (3) Sigma(+) + state are observed with an optical-optical double resonance technique. High resolution spectra are sensitively detected with the combination of perturbation facilitated polarization spectroscopy with frequency modulation spectroscopy. An electronically excited state, the B (II)-I-1 state, is mixed with the c (3) Sigma(+) State through spin-orbit interaction. The transition from the X (1) Sigma(+) state to the a (3) Sigma(+) State through the B 1II state is facilitated by the perturbation by the c(3) Sigma(+) state. Hyperfine structures of the a (3) Sigma(+)(v = 3-16,N = 4-25) state are resolved with this spectroscopic technique and found to be independent of vibrational and rotational quantum number. The a (3) Sigma(+) state can only be perturbed by the X(1) Sigma(+) state through the hyperfine interaction. The vibrational levels (v less than or equal to 16) of the a (3) Sigma(+) State are demonstrably not perturbed by the X(1) Sigma(+) state. The potential curve of the a (3) Sigma(+) state is determined by the near-dissociation expansion fitting of molecular constants and the inverse perturbation analysis method. The coefficients C-6, C-8, and C-10 of the potential function are determind to be (12.75 +/- 0.15) x 10(6) cm(-1) Angstrom(6), (2.22 +/- 0.19) x 10(8) cm(-1) Angstrom(8), and (1.100 +/- 0.061) x 10(10) cm(-1) Angstrom(10), respectively. The dissociation energy, D-e, is obtained to be 207.858 +/- 0.019 cm(-1), which is 2.8 cm(-1) above the highest observed vibrational level (v =16). determined

Hole burning in the proton NMR line in water was observed in well-defined noise fields. The hole shape was measured in two-state and Gaussian noise fields. The jumping-time dependences of the hole shape were well explained by the theory of motional narrowing and the conventional stochastic theory of relaxation. This approach is very useful for the experimental test of relaxation theories.

Phase relaxation times of proton NMR in water were measured in a well-defined noise field to test relaxation theories. Here two-state pulse noise was studied. The applicability of the conventional stochastic theory was examined, and a nonlinear theory, which well explains the experimental results, was developed.

The sub-Doppler high resolution excitation spectrum of NaRb was measured by selectively monitoring the fluorescence intensity from perturbed levels to the (1)3SIGMA+ lower state. Many transitions were observed to the (2)3SIGMA+ state perturbed by B1PI. Energy shifts of the perturbed levels were analyzed and the spin-orbit coupling constant between the (2)3SIGMA+ and B1PI states was determined, together with molecular constants of each state. Fully resolved hyperfine splittings, induced by the coupling of electron spin with both Na-23 and Rb-85 nuclear spins, were observed in the transitions. By analysis of the observed splittings, the mechanism of perturbation was confirmed as due to Fermi contact interaction and hyperfine constants of the Na-23 Rb-85 (2)3SIGMA+ state were determined. The ratio of electron spin densities at Na-23 and Rb-85 in the (2)3SIGMA+ state is estimated to be 0.84:0.16.

A collimated cesium beam is crossed at right angles by the laser beam, and the excitation spectrum of the D 1SIGMA(u)+-X 1SIGMA(g)+ transition is measured by detecting the emission from the dissociated atom Cs(6p P-2(3/2)). Line broadening is observed for a number of transitions to the D 1SIGMA(u)+ (v, J) levels, and the line shapes of the isolated lines are observed to be Lorentzian. When an external magnetic field H is applied parallel to the electric vector of the laser light, the linewidths are observed to increase proportionally to H-2, and it is attributed to the magnetic predissociation. Some lines are observed to change by the magnetic field from a Lorentzian to an asymmetric line shape accompanied by energy shift of the intensity maximum, and it is identified as originating from the M dependence of both the transition moment [D1 SIGMA(u)+\mu\ X 1SIGMA(g)+] and the Zeeman energy of the 3PI(u) state.

The Doppler-free high resolution laser spectroscopy of Cs2 D1SIGMA(u)+-X1SIGMA(g)+ transition is extended up to v' = 65. By comparing the spectral linewidth and the time-resolved fluorescence intensity, the line broadening observed for transitions to the D1SIGMA(u)+(v' = 63,J' less-than-or-equal-to 70) levels is identified as the lifetime broadening originating from the predissociation. Line splittings are observed for the D 1SIGMA(u)+(v' = 46,J' greater-than-or-equal-to 95)-X1SIGMA(g)+(v'' = 1,J'') transitions and are identified as the hyperfine splitting due to a magnetic dipole interaction between nuclear spin and electron. The hyperfine splitting is attributed to mixing of the (2) 3PI(u) state, whose wave function changes from Hund's case (a) to case (b) at large J. The dependence of the electric dipole transition moment on the internuclear distance for the D1SIGMA(u)+-X1SIGMA(g)+ transition is determined by comparing the observed and calculated line intensities of the dispersed fluorescence.

The hyperfine structures of the NaK a 3SIGMA+ state are observed for the first time by using a Doppler-free spectroscopy named perturbation facilitated polarization (PFP) spectroscopy. The hyperfine constants A(Na) and A(K) of the a 3SIGMA+ (v = 4, 5, 9, and 12) levels are determined. The observed hyperfine splittings are found to be well explained by the Fermi contact interactions of an electron spin with the sodium and potassium nuclear spins. The intensities and signs of the PFP spectra are calculated by using the determined hyperfine constants, and the results also agree with the observed ones. From the width of the observed spectra, energies of the spin-spin and spin-rotation interactions are obtained to be <5 X 10(-3) and 5 X 10(-5) cm-1, respectively.

We report on the generation of continuous-wave coherent phonons (ultrasonic waves) in ethanol by the laser-induced transient-grating method with a continuous-wave mode-locked argon-ion laser. We detected the phonons phase sensitively by monitoring the Bragg diffraction of a probe beam. Sharp resonance enhancement of the induced phonons was observed when the repetition rate of the excitation pulses coincided with the phonon frequency (the sound velocity divided by the grating period). The signal intensity was much increased as a result of interference with the co-induced thermal grating.

We measured the picosecond time-resolved fluorescence intensity following the excitations to the v'= 3, 27, and 47 levels of the D1-SIGMA(u)+ state of the CS2 molecule. When an external magnetic field was applied, a large change of the decay profiles was observed for the excitations to the v' = 27 and 47 levels, but no change for the excitation to the v'= 3 level. These results are analyzed on the basis of spectroscopic data and theoretical studies. The shortening of the lifetime by application of a magnetic field is identified as originating from the magnetic predissociation, which is caused by a combination of the spin-orbit interaction between the D1-SIGMA(u)+ and (2) 3-PI(u) states and the electronic Zeeman interaction between the (2) 3-PI(u) and (3) 3-SIGMA(u)+ states. The inner potential curve of the (3) 3-SIGMA-u+ state decomposes diabatically into the Cs(6P-2(3/2)) and Cs(6S-2(1/2)) atoms.

Scanning the frequency of a single-mode dye laser crossed with a molecular beam of NaK, we have measured the excitation spectrum by monitoring selectively the fluorescence intensity of transition to the a (3)SIGMA+ state. The B (1)PI(upsilon = 8) and (3)SIGMA+ (upsilon = 22) levels are perturbed around J = 5 and the c (3)SIGMA+ (upsilon = 22) and b (3)PI(upsilon almost-equal-to 62) levels are perturbed around J = 24. The transition lines to the perturbed levels are fully resolved. The hyperfine splitting, which is induced by the coupling with the nuclear spins of the Na and K atoms, is observed for levels of the c (3)SIGMA+ state and the perturbed states. The magnitude of the hyperfine splitting, the line intensity, and the energy shift are analyzed, and their relation with the perturbation is studied. The ratio of electron spin densities at the sodium and potassium atoms in the c (3)SIGMA+ state is estimated to be 0.71:0.15 from the magnitudes of hyperfine splitting.

Zeeman spectra of the strongly perturbed lines between the B (1)PI and c (3)SIGMA+ states of Nak were measured by the Doppler-free laser polarization spectroscopy. Magnetic field dependence of the Zeeman pattern was studied and the line shapes were found to change remarkably because of the mixing of the B (1)PI and c (3)SIGMA+ states. The patterns of Zeeman splitting were found to be different depending on whether the level was located on the high energy side or the low energy side of the interacting level. The observed Zeeman spectra were studied by taking account of the spin-orbit, hyperfine, and Zeeman interactions. The Zeeman spectroscopy is shown to be useful to analyze the perturbation between the excited states.

A newly constructed single-frequency, autoscan laser spectrometer operating in the ultraviolet in combination with a collimated molecular beam has been used to obtain a high resolution fluorescence excitation spectrum in the region 30 850-31 400 cm-1. Eight hundred and seventy five rotational lines of the Li-7(2) C 1-PI-u(upsilon' = 2-8)-X 1-SIGMA-g+ and (LiLi)-Li-6-Li-7 C 1-PI(upsilon' = 2-4)-X 1-SIGMA+ transitions are assigned. The molecular constants of the C 1-PI-u state are determined and the potential curve is constructed using the Rydberg-Klein-Rees (RKR) method. By comparing the calculated Franck-Condon factors with the line intensities of the dispersed fluorescence spectrum, we determine the dependence of the electric dipole transition moment on the internuclear distance.

High resolution spectrum of the B 1-PI-X 1-SIGMA+ transition of the NaRb molecule was measured with the technique of the Doppler-free laser polarization spectroscopy. Molecular constants of the B 1-PI(upsilon = 0-12) and X 1-SIGMA+ (upsilon = 0-6) states of Na-23 Rb-85 were determined. The energy levels of the B 1-PI state were found to present many irregularities due to perturbations. The resonance fluorescence spectrum following an excitation to a strongly perturbed level was measured. The fluorescence to the (1)3-SIGMA+ state, which consists of discrete lines followed by a continuum band, was observed in addition to the fluorescence lines to rovibrational levels of the X 1-SIGMA+ state. The perturbing state to the B 1-PI(upsilon = 8,J = 15-21) levels is identified as the (1)3-PI state by comparing the observed fluorescence spectra with the selection rules for perturbations and radiative transitions. The dissociation limit of the (1)3-SIGMA+ state, which separates into the Na(3s2S1/2) + Rb(5s2S1/2) atoms, was deduced from the spectrum. The dissociation energies of the X 1-SIGMA+, (1)3-SIGMA+, and B 1-PI states were determined to be 5030 +/- 2, 182 +/- 2, and 1319 +/- 2 cm-1, respectively.

Enhanced coherent phonons (ultrasonic waves) produced by periodic excitation of transient grating with light pulses from a Q-switched and mode-locked laser were observed when the resonance condition v=nf was satisfied, where v is the phonon frequency, f the repetition frequency of the pulses and n an integer. The enhancement was observed for phonons with frequencies from 81.8 MHz to 654 MHz, and the maximum enhancement was about 100 in intensity. The dynamics involved was analyzed by developing the theory conforming to our experimental condition. Sound velocities and phonon intensities were measured in ethanol etc. containing a small amount of dye. © 1990.