Dieter Zimmermann

Determination of the Na–Kr interaction potential in the XΣ and AΠ state by laser spectroscopy

We have extended our previous laser spectroscopic investigation of the AΠ–XΣ transition of the van der Waals molecule NaKr84. Our experimental data consist now of about 1300 absorption lines and of the spectral intensity distribution of the fluorescence light. Spectroscopic parameters have been derived for the vibrational states 0,...,2 of the XΣ state and 7,...,14 of the AΠ state. The interatomic potentials of the XΣ and the AΠ states have been determined in a fully quantum‐mechanical approach using analytical HFD or Tang–Toennies functions. For the equilibrium distance and the well depth we obtain 4.918(4) A, 68.4(5) cm−1 for XΣ and 3.03(4) A, 3.05(4) A and 795(25) cm−1, 760(20) cm−1 for AΠ1/2 and AΠ3/2, respectively.

Investigation of J dependence of line shift, line broadening, and line narrowing coefficients in the ν1+3ν3 absorption band of acetylene

Line shift coefficients, line broadening coefficients, and line narrowing coefficients have been measured in the ν1+3ν3 band of acetylene using a diode laser system operating at 788 nm and a multipass Herriot absorption cell. Experimental data have been obtained for 20 lines of the P and R branches broadened by N2, O2, air, and the rare gases He, Ne, Ar, Kr, and Xe. The observed line shapes could successfully be reproduced by employing Galatry and Rautian functions which include the phenomenon of Dicke narrowing. Our results for the line broadening coefficients are in good agreement with the values reported previously for other vibrational bands. Thus, the present work confirms the vibrational independence of the broadening coefficients. On the other side, we observed a clear dependence of the narrowing coefficients on rotation in a vibrational transition of acetylene for the first time. In addition, the line center frequencies have been determined with improved accuracy.

A Re-Evaluation of Isotope Shift Constants*

The field isotope shift constantCunif for a uniform nuclear charge distribution has been re-evaluated fors-electrons for elements with 10≦Z≦ 95. A table is given which permitsCunif to be found for any isotope pair.

Laser spectroscopic investigation of the van der Waals molecule NaXe

Abstract The electronic transition A 2 Π ← X 2 Σ of the van der Waals molecule NaXe has been investigated by means of high-resolution laser spectroscopy in a supersonic jet. By applying the method of optical-optical double-resonance, a rotational analysis could be performed for the three isotopomers Na 129 Xe, Na 131 Xe, and Na 132 Xe. Spectroscopic parameters have been derived for the vibrational levels 0 of the X Σ state and 10–16 of the A Π states. In addition, the spectral distribution of the fluorescence light has been observed. The interatomic potentials of the X Σ and the A Π states have been determined from the experimental data by means of a quantum-mechanical method of approach using analytical Tang-Toennies, Thakkar, or HFD functions. For the equilibrium distance and the well depth we obtain 4.95(4) A, 3.20(5) A, 3.22(5) A, and 117(15) cm −1 , 1215(35) cm −1 , and 1120(35) cm −1 for X Σ, A Π 1 2 , and A Π 3 2 , respectively.

Laser spectroscopic investigation of the van der Waals molecule NaKr84

The absorption spectrum of the van der Waals molecule NaKr due to the transition X 2Σ→A2Π has been observed with high resolution using a tunable single‐mode cw dye laser and producing the molecules by means of supersonic expansion. About 600 lines due to the most abundant Kr‐isotope Kr84 have been analyzed. The spectroscopic parameters of molecular rotation, of fine structure splitting and of λ‐type doubling have been obtained for the vibrational levels v’=10⋅⋅⋅14 of the A 2Π state and for the level v‘=0 of the X 2Σ state. The experimental positions of the band origins of the vibrational transitions are in satisfactory agreement with the results of model potential calculations. The equilibrium distances of the X 2Σ and of the A 2Π state of NaKr84 have been determined to be 4.919(7) and 3.02(9) A, respectively. For the well depth we obtain values of (69±4), (790±60), and (750±60) cm−1 for X 2Σ, A 2Π1/2, and A 2Π3/2, respectively.

Observation of spin-polarized atomic photofragments through the Doppler-resolved Faraday technique

The angular distribution of spin-oriented Rb photofragments produced by photodissociation of RbI molecules using circularly polarized UV light at 266 nm has been investigated for the first time applying the method of Doppler-resolved paramagnetic Faraday rotation. The observed signals could successfully be explained as the sum of two contributions being due to incoherent and coherent excitation of the RbI molecules. For the ratio of the two corresponding anisotropy parameters we obtain a value of −0.33 as a preliminary result.

Laser spectroscopic investigation of the X 2Σ1/2 state of the van der Waals molecule NaAr

Abstract The laser-excitation spectrum of the transition X 2 Σ + → A 2 Π of NaAr has been investigated using a supersonic expansion of a mixture of sodium vapor and argon gas for production of the molecules. In comparison to preyous investigations the rotational constants of the vibrational levels ν″ = 2, 3 and 4 of the X 2 Σ + state could in addition be determined. From our results we deduce a value of R e = 5.008(5) × 10 −10 m for the equilibrium internuclear distance and of D e = 41.7(δ) cm −1 for the well depth of the X 2 Σ + state.

High-resolution laser spectroscopy of the A ← X transition of LiAr

Abstract The rotationally resolved absorption spectrum of LiAr due to the transition A 2 Π ← X 2 Σ has been investigated by laser spectroscopy producing the molecules in a supersonic jet beam. Vibrational levels with ν = 0,…, 3 and ν = 5,…, 9 have been observed up to now for the X 2 Σ and the A 2 Π state, respectively. The XΣ interaction potential has been determined by means of a quantum mechanical method using a Hartree-Fock dispersion function. For the well-depth and equilibrium distance of XΣ. we obtain D e = 42.5(1.2) cm −1 , R e = 4.888(15) A . Our preliminary results for the A 2 Π state are: D e = 925(40) cm −1 , R e = 2.48(6) A .

Determination of the K–Ar interaction potential in the XΣ and AΠ state from laser spectroscopic data

The absorption spectrum of the van der Waals molecule KAr has been recorded between 12 870 and 13 040 cm−1 by means of high‐resolution laser excitation spectroscopy in a supersonic jet expansion. About 1600 molecular absorption lines could successfully be assigned to the rovibrational structure of the electronic transition A 2Π←X 2Σ+ of 39KAr. In addition, a few absorption lines due to the isotopomer 41KAr have been detected. Spectroscopic parameters have been obtained for vibrational levels 0...3 of X 2Σ+ and 6...11 of A 2Π. Additional experimental information was provided by observing the spectral distribution of the fluorescence. The interatomic potentials of the X 2Σ+ and the A 2Π states have been derived from the experimental data by means of a fully quantum‐mechanical approach using suitable analytical functions. Our final results for equilibrium distance Re and well‐depth De are 5.404(5) A and 40.1(6) cm−1 for X 2Σ+, 3.37(3) A and 405(15) cm−1 for A 2Π1/2, and 3.34(3) A and 427(15) cm−1 for A 2Π3/2...

Level-crossing-Untersuchung der Hyperfeinstruktur des angeregten 32P3/2- und 42P3/2-Zustands von Na23

The hyperfine structure of the excited 32P3/2- and 42P3/2-state of Na23 has been investigated in a level-crossing-experiment by means of a detailed analysis of the dependence of the scattered resonance light as a function of the magnetic field. From the experimental curves the following results for the hyperfine structure constantsA andB and for the lifetimesΤ were deduced 32P3/2-state: 42P3/2-state:A=18.65(10)Mc/sA=6.006(30)gj/1.334Mc/sB=2.82(30)Mc/sB=0.86 (9)gj/1.334Mc/sΤ=1.60 (3) · 10−8sΤ=6.56 (25)1.334/gj·10−8 s.The nuclear electric quadrupolemoment of Na23 derived from these values isQ=0,097 · 10−24 cm2, where the Sternheimer-correction has been applied.