C.T. Scurlock

A supersonic molecular beam optical Stark study of CaOH and SrOH

The permanent electric dipole moments of CaOH and SrOH in their X 2Σ+, A 2Π3/2, A 2Π1/2, and B 2Σ+ states have been measured using the technique of supersonic molecular beam optical Stark spectroscopy. For CaOH the values obtained were μ(X 2Σ+)=1.465(61)D, μ(A 2Π1/2)=0.836(32)D, μ(A 2Π3/2)=0.766(24)D, and μ(B 2Σ+)=0.744(84)D, while for SrOH the values were μ(X 2Σ+)=1.900(14)D, μ(A 2Π1/2)=0.590(45)D, μ(A 2Π3/2)=0.424(5)D, and μ(B 2Σ+)=0.396(61)D. The results are compared with values from a recent ab initio calculation for CaOH and with the predictions of a semiempirical electrostatic polarization model.

Hyperfine interactions in the ground states of titanium monoxide and mononitride

A comparative study of the hyperfine interactions in the X 2Σ+ state of TiN and the X 3Δ state of TiO has been performed. The 48Ti14N(I=1) hyperfine structure was determined from the analysis of 19 components of the N=1–0 and N=2–1 pure rotational transitions recorded using the pump/probe microwave‐optical double resonance technique. The 47Ti(I=5/2) hyperfine structure of X 2Σ+ TiN was determined from an analysis of the high resolution optical spectrum of the (0,0) A 2Π3/2–X 2Σ+ band system. The resulting parameters are (in MHz) B(48Ti14N)=18 589.3513(13), D(48Ti14N)=0.026 31(18), γ(48Ti14N)=−52.2070(13), bF(N)=18.480(3), c(N)=0.166(7), eQq0(N)=−1.514(8), CI(N)=0.0137(12), bF(47Ti) =−558.8(11), c(47Ti)=−15(5), and eQq0(47Ti)=62(16). An analysis of the (0,0) band of the B 3Π–X 3Δ system of 47Ti16O produced the X 3Δ hyperfine parameters (in MHz): a(47Ti) =−54.7(21), (bF+2c/3)(47Ti)=−231.6(60), and eQq0(47Ti)=−49(31). An interpretation based upon the predicted nature of the bonding in TiO and TiN is given.

MOLECULAR BEAM PUMP/PROBE MICROWAVE-OPTICAL DOUBLE RESONANCE USING A LASER ABLATION SOURCE

The first successful pump/probe microwave‐optical double resonance experiment using a laser ablation/reaction scheme for molecular beam production has been performed. Pure rotational transitions at frequencies up to 52 GHz have been recorded for the transient refractory compounds YF, YO, and SrOH at a resolution of <30 kHz [full‐width at half‐ maximum (FWHM)]. The observed three lowest pure rotational transition frequencies of YF (X 1Σ+) were analyzed to produce an improved set of rotational constants, B=8683.6156(11) MHz and D=0.007 521(74) MHz. The three lowest pure rotational transitions of SrOH (X 2Σ+) were analyzed to give the spectroscopic parameters (in MHz), B=7470.8180(4), D=0.006 25(3), γ=72.706(1), γD=−0.0021(2); bF (H)=1.713(2) and c (H)=1.673(5). The proton magnetic hyperfine interactions were interpreted in terms of a molecular orbital description for the X 2Σ+ state.

Molecular beam optical Stark spectroscopy of calcium monocyanide

The 617.7 and 614.7 nm bands of calcium monocyanide, CaNC/CaCN, have been recorded at high resolution by laser‐induced fluorescence using a supersonic molecular beam. The two bands consist of twelve branches that are assigned to a case a (0,0,0)A 2Πr–(0,0,0)X 2Σ+ transition. A reduction of the data to an effective Hamiltonian model produced the spectroscopic parameters (cm−1): T00= 16229.5417(26), B″=0.13499(14), γ″=6.1837(33)×10−4, A′=77.6451(40), B′=0.15027(23), AD′=2.69(11) × 10−3, D′= −3.50(25) × 10−5, p′=0.0754(18), q′=−0.04808(87), qD′′= 2.64(65) × 10−5. It is proposed that the anomalous values of the excited state parameters arise because of Renner–Teller interactions. The magnitude of the permanent electric dipoles, |μ|, were also determined and are 5.949(1) D[A 2Π1/2(0,0,0),J= 0.5] and 6.895(9) D[X 2Σ+(0,0,0),J= 1.5]. The large value of |μ| is consistent with an isocyanide structure, CaNC. A comparison with theoretical predictions is presented.

The pure rotational spectrum of CaNC

The pure rotational spectrum of calcium isocyanide, CaNC, in its (0,0,0) X 2Σ+ vibronic state was measured using a combination of Fourier transform microwave (FTMW) and pump/probe microwave‐optical double resonance (PPMODR) spectroscopy. Gaseous CaNC was generated using a laser ablation/supersonic expansion source. The determined spectroscopic parameters are (in MHz), B=4048.754 332 (29); γ=18.055 06 (23); bF=12.481 49 (93); c=2.0735 (14); and eQq0=−2.6974 (11). The hyperfine parameters are qualitatively interpreted in terms of a plausible molecular orbital descriptions and a comparison with the alkaline earth monohalides and the alkali monocyanides is given.

A microwave-optical double resonance spectroscopic study of TiO and TiN

Abstract The J = 2 ← J = 1 and J = 3 ← J = 2 pure rotational transitions of TiO ( X 3 Δ) and the N = 2 ← N = 1 pure rotational transition of TiN ( X 2 Σ + ) have been recorded using the technique of microwave-optical double resonance (MODR) spectroscopy. There was no evidence of Λ-doubling in the spectra of TiO and no evidence of hyperfine splitting in the spectra of TiN. An improved set of spectroscopic parameters for the ground state of these two molecules is given and are used to predict the pure rotational transition frequencies associated with low-lying rotational levels.

An analysis of the à 2Π–X̃ 2Σ+ band system of isotopically substituted calcium isocyanide CaNC

The strong visible band systems of a supersonic molecular beam sample of isotopically substituted CaNC (13C and 15N individually) have been recorded at high resolution by laser‐induced fluorescence spectroscopy. The spectra have the general appearance of the expected A 2Π–X 2Σ+ band systems, but the energy levels of both the ‖Ω‖=1/2 and 3/2 excited substates have localized perturbations. Spectroscopic parameters for the X 2Σ+ state of the isotopomers were extracted from a least‐squares fit to the appropriate combinations differences of the observed transitions frequencies. Excited state effective parameters were extracted by directly fitting the unperturbed portions of the optical spectra. The rs‐structure bond lengths for the ground electronic state were determined to be Ca–N=2.2065(58) A and N–C=1.1186(58) A. The permanent electric dipole moments for the Ca15NC isotopomer were determined to be 5.93(8) and 6.69(9) D for the A 2Π and X 2Σ+ states, respectively.

Refractory radicals generated by pick-up molecular beam techniques

Abstract A new method of the generation of “cold” molecular beam samples of high temperature refractory compounds is described. The method combines the simplicity of an electron bombardment effusive oven for the generation of refractory compounds with the advantage of supersonic expansion. The applicability of the technique is de monstrated by recording the high-resolution laser-induced fluorescence (LIF) spectra of the (0, 0) B 2Σ+−X 2Σ+ (ν00=16855.14 cm−1) band system of CaCl. A comparison with the LIF spectra for a molecular beam sample of CaCl generated by conventional effusive oven techniques is made.