P. Jungner

LASER INDUCED VIBRATION-ROTATION FLUORESCENCE AND INFRARED FORBIDDEN TRANSITIONS IN ACETYLENE

Laser induced fluorescence method has been used to study highly excited vibrational overtones in acetylene. A sample cell has been placed inside a Ti:Sapphire ring laser cavity and the total fluorescence collected by a parabolic mirror has been dispersed by a high-resolution FTIR spectrometer. The laser has pumped specific rotational states of the CH stretching vibrational overtone state ν1+3ν3(∑u+) and transitions to the symmetric state ν1+2ν3(∑g+) have been observed. The observations allow determining both the vibrational term value and the rotational constant of the symmetric state, which is not accessible from the ground vibrational state by one-photon absorption. The parameters obtained are in excellent agreement with simple local mode predictions.

Nonlinear forward scattering of resonant laser light from excited neon systems

We investigate forward scattering induced by a powerful single mode dye laser interacting with excited neon systems. We present experimental data obtained with the three transitions: 1s4(J=1)-2p3(J=0), 1s2(J=1)-2p1(J=0), and 1s5(J=2)-2p4(J=2). The lineshape dependences on the gas pressure, the laser power and the laser field fluctuations are discussed in the context of published theories. Our data resemble the calculated lineshapes in which fluctuations in the interaction processes between atoms and laser fields are taken into account. In atomic systems having more complex level degeneracies [1s5(J=2)-2p4(J=2)] signal structures expected from higher order nonlinear coherences can occur. To theoretically reproduce these lineshapes a simple J=1→J=0 model is fully appropriate provided that the level with J=1 has a narrow width.

Measurements of absolute transition probabilities in Ba ii through optical nutation: erratum

We have developed a method to measure absolute transition probabilities for ions by recording optical nutation. Ions in an accelerated beam are brought into resonance with a counterpropagating laser beam by a rapid Doppler switch. From the time evolution of the population of the upper level in the resonant transition, we determine the Rabi frequency of the transition. An accurate measurement of the electric field strength then yields the transition probability. We report measurements for five transitions in Ba ii. For three of these transitions our values are more accurate than those of earlier published results.

Forward scattering induced by laser fields in atomic J=1→J=0 systems

Abstract We investigate resonant forward scattering of laser radiation. Calculations based on the semiclassical laser theory are performed up to the second order in the laser intensity. The response of the atomic J =1→ J =0 transition to a laser beam is considered. Experimental verification of the theoretical lineshapes is carried out using a neon gas absorber. The agreement between the calculated results and the measurements is excellent and indicates that higher order nonlinearities such as hexadecapole couplings are not easily discerned in the lineshapes.

Stabilization of a single mode dye laser to a HeNe laser using magnetic modulation of a three-level neon system

Abstract We describe a simple stabilization method where a tunable single mode (594.5 nm) cw dye laser is locked to a stabilized (633 nm) HeNe laser via the 1s 5 -2p 4 -3s 2 Ne transitions. By using longitudinal Zeeman modulation of the absorber and a circularly polarized HeNe laser beam derivative signals are obtained. Utilization of routine lock-in techniques produces a dye laser frequency stability comparable with that of the reference HeNe laser.

A very simple stabilized single‐mode He–Ne laser for student laboratories and wave meters

The principle and the construction of an intensity and a frequency‐stabilized single‐mode internal mirror He–Ne 633‐nm laser are described. An intensity stability better than 10−3 and a frequency stability better than 10−8 are obtained. The design is very simple, and the system is recommended for student laboratories and for laser‐wavelength meters.

Collision-induced resonances in Doppler-broadened systems

Abstract This paper discusses the occurrence of collision-induced resonances in a Doppler broadened system. They consist of a narrow coherent signal and a broad population transfer signal. The latter has a strength proportional to the rate of phase perturbing processes. The specific example of Hanle level-crossings is discussed in detail. The disappearance of the broad resonance is shown to derive from cancellation of coherent and incoherent contributions. Their origin is elucidated by a diagrammatic density matrix perturbation expansion. Finally the results are verified experimentally on the red transition in a Ne gas. The narrow and broad resonances are identified, and the ratio of their strengths is shown to disappear with the pressure in the sample cell.

Measurements of 22Ne-20Ne isotope shifts by laser-induced line narrowing in three-level systems

Application of laser-induced absorption line narrowing (ALN) to neon isotope shift investigations in the stretched three-level systems 1s5-2p4-3s2 and 1s4-2p4-3s2 is reported. The measurements have been performed with a frequency and intensity-stabilized 633-nm He-Ne probe laser and with a tunable single-mode R6G dye laser. Utilization of longitudinal magnetic modulation to the neon gas absorber yields background-free resonance signals. Measurements of 594.5-, 609.6-, and 633-nm 22Ne-20Ne isotope shifts result in (1712 ± 8) MHz, (1753 ± 8) MHz, and (904 ± 8) MHz, respectively. These values agree with previous data.

Laser induced polarization properties of a neon three-level system

Abstract We investigate polarization spectroscopy as a probe of broken left-right symmetry in neon atoms. In the cascade 1s 4 -2p 4 -3s 2 three-level system the upper transition is probed by a linearly polarized weak HeNe laser beam. The symmetry of the lower level is broken by a circularly polarized strong dye laser beam acting on the lower transition. We present the experimental setup, the resulting measurements and a comparison with a straightforward theory of symmetry breaking.

Construction and alignment of a compact wavelength meter for cw lasers

Abstract We describe a simple and reliable automatic fringe-counting interferometer featuring a real-time display of cw laser wavelengths. The wavemeter and its reference laser constitute a compact construction and offer easy operation. The accuracy of the system is better than one part in 106.