T. A. Wiggins

Production and uses of diffractionless beams

It is proposed to obtain intense optical fields, whose form shows little change in size over long paths, through the use of either conical lenses or spherical lenses showing spherical aberration together with a single projecting lens. The conical lens is shown to produce fields whose transverse structure is given by a zero-order Bessel function J0, while the spherical aberrating lens produces (real or virtual) J0-like transverse structures, provided that the central portion of the aberrating lens is occluded. In all cases projection gives a J0 real-image optical structure. Intensity, size of the transverse structure, and range considerations are developed, and some aspects of optimization are discussed. A negative aberrating lens gives a long range of nearly constant size in the image field, and a universal expression is presented to describe the image size as a function of image distance for this case. Projection with an aberrating projection lens is shown to improve the constancy of the final J0 pattern size dramatically. Typical photographic results are included for beams generated by using a low-power He–Ne laser. Brief considerations of practical uses of diffractionless beams are presented.

Molecular constants of HCl35

Abstract Additional measurements have been made on the 1-0 and 2-0 bands of HCl 35 . The spectra were observed using an absorption tube heated to 900°C. Rotational states involving J ″ values as high as 31 were observed. In addition, lines of the 3-1, 4-2, and 5-3 bands have been observed and precisely measured. The newly observed data have been combined with our previously reported measurements on HCl 35 and analyzed. Reliable values have been obtained for the higher order rotational constants, H and L . The Dunham potential constants a 1 , a 2 , a 3 , and a 4 for HCl 35 have been calculated.

Frequency and intensity measurements on the quadrupole spectrum of molecular hydrogen

Abstract The quadrupole spectrum of molecular hydrogen has been investigated with spectroscopic instruments of high resolution and a large 44-meter multiple reflection absorption cell. The frequencies of seven lines in the 1-0 band and two lines in the 2-0 band were measured. Pressure shifts were obtained for five lines in the 1-0 band. These data were used to obtain precise molecular constants for the first few vibrational states. Intensity measurements on the lines of the 1-0 and 2-0 bands and the S(1) line of the 3-0 band were made and corrected by means of an empirical curve of growth. These measurements are compared with theoretical calculations of the hydrogen quadrupole matrix element.

Breadths and shifts of molecular band lines due to perturbation by foreign gases

Abstract The shifts in frequency and the half-intensity widths (HIW) due to foreign gases have been measured in the fundamental bands of HCl 35 , DCl 35 , and HBr 79 , and in the 1-0 and 2-0 bands of CO. The salient features of these effects are the linear dependence of shifts and widths upon the density of the foreign gas, the strong J dependence, and the dependence of the maximum shift observed upon the vibrational quantum number of the band and the polarizability of the foreign gas. The results are in agreement with similar earlier work.

Rotational and Vibrational Constants of the HCl 35 and DCl 35 Molecules

The 1–0, 2–0, 3–0, 4–0, and 5–0 bands of HCl35 and the 1–0 and 2–0 bands of DCl35 have been measured with high precision. A critical analysis has been made to determine the rotational and vibrational constants of these molecules. It is necessary to use a polynomial in m of the sixth degree to satisfactorily represent the frequencies of the band lines in the case of the most precisely measured bands. B0 for HCl35 has been found to have a value of 10.440254±0.000010 cm−1. B0 for DCl35 was found to be 5.392261±0.000010 cm−1. When the B0 obtained for DCl35 is combined with the microwave measurement of B0 by Cowan and Gordy the value obtained for the velocity of light c=299 793.1±0.65 km/sec. The observed rotational and vibrational constants (Ylj) have been used to calculate the potential constants of HCl35 by making use of Dunham’s theory of a rotating vibrator. It is shown that HCl35 is not a pure rotating vibrator since the observed and calculated values of Y02~De are in disagreement by about 1 part in 1000 which is approximately 10 times the experimental error. By making use of the molecular constants for HCl35 and DCl35 and the accurately known atomic masses it is deduced that the ground level Be is perturbed by the upper electronic levels by 1 part in 8000. The sign of the perturbation is to increase Be over its unperturbed value. The sign of the perturbation is such that it may be presumed the HCl molecule has a positive magnetic moment. It was calculated that μJ=+0.2 and +0.1 nuclear magnetons, respectively, for HCl35 and DCl35.

Determinations of some hydrogen molecular constants

Abstract This paper reports an investigation of pressure perturbations of the fundamental rotation-vibration band of hydrogen. Both the electric field induced dipole spectrum and the stimulated Raman spectrum of hydrogen have been used to measure spectral line frequencies at gas densities extending up to 280 amagat. Linear pressure shifting coefficients have been obtained for the lines Q (0), Q (1), Q (2), Q (3), and S (1). The quadratic pressure shifting coefficient has been determined for the line Q (1). These data were combined with spectroscopic data available in the literature to obtain the zero density frequencies of eight lines in the 1-0 band and two lines in the 2-0 band. Precise molecular constants for the first few vibrational states were calculated. The pressure broadening coefficient and integrated absorption coefficient have been determined for the line Q (1). Experimental values of the matrix element of the expectation value of the polarizability ∥ α 01 ∥ and the matrix element of its anisotropy ∥ γ 01 ∥ have been obtained.

Highly Precise Wavelengths in the Infrared. II. HCN, N 2 O, and CO†

A discussion is given of the effect of mechanical errors in a grating drive on the accuracy with which line frequencies can be measured. It is shown that it is highly improbable that a mechanical device used to rotate a diffraction grating can be constructed with sufficient precision so that the line-frequency error will be determined by the optical information observable in the near infrared spectrum. By making use of the echelle spectrograph 67 lines of the 001–000 absorption band of HCN have been measured. Almost 400 lines from five N2O absorption bands arising from the ground state of the molecule have been measured. In addition, 11 lines from the 1–0 fundamental band of CO have been measured in order to determine ν0 for this band. In all cases only band lines have been measured which appear to be free of blends. The molecular constants of the above bands have been determined by making use of the combination relationships applying least-squares methods to the data. The line frequencies have then been calculated to four decimal places and presented in tables. The tables contain over 600 line frequencies. We believe the calculated line frequencies (lines free of blends) have an absolute accuracy of about 1 part in 5×106 and a relative accuracy referring to lines within a given band somewhat greater.

Vibration-Rotation Spectra of HCN†

An analysis of the spectrum of the linear unsymmetric molecule HC12N has been made permitting the determination of the 21 constants necessary for predicting the vibrational frequencies and the 10 constants necessary for predicting the B value for the various vibrational states. To determine these constants new measurements were made on numerous bands in the region of 1–3 μ employing a 5-m vacuum spectrograph. Several instances of Fermi resonance were detected and analyzed. Except for a few bands where additional resonances may be present, the vibrational constants predict the measured values for the band origins of 44 bands within an amount not much greater than the expected experimental error. The rotational constants also predict the B value within the experimental error for 24 bands where data are available.Bands of HC13N and DC12N were also measured to determine the α values for calculation of the equilibrium moment of inertia. The 101–000 and 1111–0110 bands were used for all three isotopic forms of HCN to determine the Be values in a parallel fashion. From these values the bond length C–H=1.06593±0.00010 A and C–N=1.15313±0.00002 A were determined.In five different cases in HC12N it was possible to apply the Ritz combination principle to determine the frequency of the 0110 state. By using this value and the rotational constants it was possible to calculate the frequencies of lines in the 0110–000 band. The principle is also applied to HC13N and DC12N.

ROTATION-VIBRATION CONSTANTS OF ACETYLENE

The study of the absorption spectrum previously reported has been extended to include the 1900- to 2200- and the 4400- to 6750-cm−1 regions. Rotational analysis provides 20 states from which the following constants are determined: α1 = 6.82, α2 = 6.30, α3 = 5.60, α4 = −1.30, α5 = −2.20 × 10−3 cm−1 and Be = 1.18240 cm−1. This value was used with Be values for C2HD and C2D2 to determine the bond length of re(C−H)=1.0603 and re(C≡C)=1.2034A.A total of 46 states was available, from this and other work, to determine a set of vibrational constants. About one-half of the 23 constants have been determined with acceptable precision. The remaining constants are still in doubt due, primarily, to resonances.

High resolution measurements on the infrared absorption spectrum of HBr

Abstract Wavelengths of 39 lines in the 1-0 band, 43 lines in the 2-0 band, and 27 lines in the 3-1 band of HBr 81 were precisely measured. From these lines and Gordys microwave data very accurate molecular constants for HBr 81 were obtained. Isotope differences of HBr 79 HBr 81 for the same three bands were also measured and were shown to agree with the values calculated from mass spectroscopic data.