Kiyoji Uehara

Stark Effect of the Absorption Line of Methane Observed by the 3.391 µm He-Ne Maser

The Stark effect in CH 4 which has no permanent dipole moment in the ground vibrational state is observed on one component line at 2947.802 cm -1 of the P (7) line in the ν 3 band by a magnetically tuned infrared maser. The effect is interpreted on the basis of the second-order induced dipole moment in the degenerate vibrational state which has the F 2 symmetry. The magnitude of the induced dipole moment of CH 4 in the ν 3 vibrational mode is evaluated from the observed Stark effect.

High-resolution Stark spectroscopy of molecules by infrared and far-infrared masers

Some of the He-Ne and He-Xe laser lines in the infrared can be tuned within several gigahertz by applying an axial magnetic field. Stark patterns of vibration-rotation lines of organic molecules were observed at 3.36-, 3.39-, 3.50-, and 5.57-μm wavelengths. With applied Stark fields up to 50 kV/cm, many Stark components were resolved and some of the transitions of H 2 CO, HDCO, and CH 4 were definitely assigned. Molecular masers in the far infrared cannot be tuned over any appreciable range, but the Stark effects of the rotation lines of NH 3 at two fixed far-infrared frequencies of the D 2 O maser were observed. The observations of a Stark component of the J = 3 \leftarrow 2 line at 171.6 μm and the forbidden Stark components of the J = 6 \leftarrow 5 line at 84.1 μm are reported.

Stark Effect of Vibration-Rotation Lines of Formaldehyde Observed by a 3.5 µm Laser

A high resolution infrared spectroscopy of the Stark effect of H 2 CO and HDCO by using a magnetically tunable infrared-maser (laser) is reported. The output frequency of the He-Xe laser centered at 2850.6 cm -1 is tuned within ±6GHz to observe Stark patterns of vibration-rotation lines of formaldehyde in the electric field up to 44 kV/cm. Some of the lines have been assigned from their Stark effects. The observed Stark shift, K -type doubling, intensity change of the forbidden transition with the Stark field, and the assignment of lines are discussed in connection with the molecular constants of H 2 CO and HDCO.

Hyperfine Interactions in the v3=1 Exited State of Methane

The magnetic hyperfine interactions in the triply degenerate vibrational state of 12 CH 4 are theoretically studied. The spin-vibration interaction is introduced as well as the spin-spin and spin-rotation interactions to obtain the explicit expressions of matrix elements of the hyperfine energy. The numerical calculations are carried out for the 6 7 F 1 (2) and A 1 sublevels in the v 3 =1 exited state and a comparison is made with a recent measurement of Hall and Borde on the F 1 (2) line.

New Method of Frequency Stabilization of Semiconductor Lasers

It is demonstrated that the frequency of a semiconductor laser driven by a constant current can be stabilized by controlling the operating temperature so as to give a constant operating voltage. Since the operating voltage is a direct monitor of the operating temperature, the frequency thus stabilized is insensitive to ambient temperature variations. For hermetically unsealed near-infrared lasers the frequency stability is within ±350 MHz under normal laboratory conditions and the shift is only 500 MHz for a 10°C variation in the ambient temperature. A resettability of ±350 MHz is obtained with an adjustment-free operation.

Electromagnetic plane waves with parallel electric and magnetic fields E∥H in free space

Maxwell’s equations for electromagnetic waves in free space, with parallel electric and magnetic fields, are solved under the condition that the fields are functions of z and t, independent of either x or y. A number of interesting examples of plane waves obtained from the general solution are shown. Their properties and the vanishing Poynting vector are discussed.

Exact Solutions in the Semi-Classical Theory of a Gas Laser for Two Special Cases

An exact expression of the gain constant of two-level molecules (or atoms) in a standing-wave optical field is obtained for a special case where the optical frequency is in exact resonance with the molecular transition and the longitudinal and transverse relaxations have equal decay constants. Secondly, an exact form of gain constant as a function of frequency detuning which decribes the shape of Lamb dip or saturated absorption is shown for another case where the transverse relaxation is much faster than the longitudinal relaxation. A flat velocity distribution of molecules at Doppler limit is assumed in either case.

Stark Effect of F1(2) Line of Methane at 3.39 µm Observed by the Method of Inverted Lamb Dip

The small Stark effect of the F 1 (2) line of methane at 3.39 µm is studied. The observed Stark pattern does not reveal resolved Stark components at the maximum applied field intensity of 40 kV/cm. But it shows a broadening of particular asymmetry and it is in satisfactory agreement with the theoretical pattern of the second-order Stark shift as given by Δ ν=5.31×10 -2 M 2 E 2 kHz where M is the quantum number for the component of angular momentum along the Stark field and E is the magnitude of Stark field in kV/cm. Thus the Stark shift of this line in a weak field is extremely small so that a high accuracy as a frequency standard can be guaranteed.

Fifth-, Seventh- and Ninth-Order Calculations of the Lamb Dip in Lasers and Saturated Absorption

The semi-classical theory of a single-mode gas laser has been extended to include higher-order terms by a simpler method than previous ones. The present theory takes not only the lifetimes of the two states but also the effect of phase-perturbing collisions into consideration by using three phenomenological decay constants in the two-level system. Explicit expressions in the general case of nonlinear susceptibility of the laser medium or the saturable absorber are presented for the fifth and seventh orders, while the ninth-order expression is shown for a special case of a very long longitudinal relaxation time.