Patrick G. Carrick

Rotational analysis of the à ← X̃ system of C2H

Precise frequencies for the observed lines of five bands of the A 2Π ← X 2Σ system of C2H are reported. These frequencies have been least‐squares fitted with an effective rotational Hamiltonian and the resulting parameters are given.

à 2Π←X̃ 2Σ+ infrared electronic transition of C2H

Five bands of the A 2Π←X 2Σ+ lowest electronic transition of C2H have been observed in the region 3600–4200 cm−1 in an argon discharge over polyacetylene using color center laser spectroscopy with magnetic rotation sensitivity enhancement. The band origins are approximately 3692, 3773, 3785, 4011, and 4106 cm−1. Rotational assignments and preliminary fittings of all five bands have been made. Four of the bands have a 2Σ+ lower vibronic state which is undoubtedly the ground vibronic state of the molecule, and different 2Π upper vibronic states which correspond to mixtures of the lowest vibronic state of the A electronic state and three different vibrationally excited levels of the X electronic state with an odd number of quanta in the bending mode and overall 2Π symmetry. These three ground state vibrational levels have been tentatively assigned as (1,1,0), (0,1,2), and (0,5,1). The four 2Π vibronic levels are mixed by vibronic coupling between the X and A electronic states thereby providing electron...

Infrared absorption spectrum of C2H radical with color center laser

P. Q. and R branches are studied for C2H free radicals. (AIP) P. Q. and R branches are studied for C2H free radicals. (AIP)

The OH strecthing fundamental of methanol

Abstract The highly congested band-center region of the OH stretching fundamental of methanol has been investigated using color center laser spectroscopy. Analysis of this region is essentially hopeless by normal absorption spectroscopy with Doppler limited resolution, but the spectral simplifications observed in Stark modulation absorption spectroscopy of the room-temperature gas and in simple absorption spectroscopy in a pulsed supersonic slit jet make possible the assignment of rotational structure in this region.

Magnetic rotation observation of the C2 b3Σg− ← a3Πu transition using a color center laser☆

Abstract The magnetic rotation observation of the C2 b3Σg− ← a3Πu Ballik-Ramsay system using a color center laser is reported. This is the first detection of this system in absorption. Three bands, 0 ← 1, 1 ← 2, and 2 ← 3, were identified in the spectral range 3650–4030 cm−1. The last two bands were observed for the first time. In magnetic rotation many satellite lines (ΔN ≠ ΔJ) which would be very weak in normal absorption have been observed with intensity comparable to the main branch lines. This permits a slight improvement in the accuracy of some of the fine structure constants. A variety of lineshapes are observed for the various branches by magnetic rotation. Because the b3Σg− fine structure is small, giving a partial overlap, the peak frequency of a magnetic rotation signal usually does not correspond to the center frequency of the normal absorption signal of that transition. A computer program has been written to predict magnetic rotation lineshapes and obtain the peak frequency displacements. Various observed and calculated lineshapes are displayed and compared.

High Sensitivity Color Center Laser Spectroscopy

The development of cw color center lasers [1] has inevitably led to their application to spectroscopy. The commercial availability of a color center laser provides ready access to this technology to any laboratory. In this paper, we wish to examine the prospects of color center lasers as tunable sources for high sensitivity infrared absorption spectroscopy, describe the development of a computer-controlled color center laser spectrometer based upon the commercial Burleigh FCL-20 laser, and report on several spectroscopic investigations using the computer-controlled color center laser.