Quantum beat study of the nuclear hyperfine structure of OD and Ar⋅OD in their A 2Σ+ electronic states

Abstract

Articles you may be interested inHyperfine structures of the 7Li2 b 3Π u , 23Π g , and 33Π g states: Continuous wave perturbation facilitated optical-optical double resonance spectroscopy A threedimensional wave packet study of ArI2(B)→Ar + I + I electronic predissociationHyperfine and Zeeman quantum beats of the Na(32 P 3 / 2-32 S 1 / 2) transition, and the decay of coherence J. Chem. Phys. 90, 5238 (1989); 10.1063/1.456477Radiative lifetime measurements of the Alu states of Ar2 and Kr2* AIP Conf.The nuclear hyperfine structure of OD and Ar•OD in their A 2 ⌺ ϩ electronic states has been studied by quantum beat spectroscopy. The very cold transient species were produced in a supersonic expansion using a pulsed discharge nozzle. Coherent excitation of hyperfine ͑hf͒ states, arising from one fine structure ͑OD͒ or rotational ͑Ar•OD͒ level, created quantum beats on the fluorescence decay. The beat frequencies, which correspond to energy separations between hf levels, could be measured to Ϯ75 kHz. The splitting of the hf levels into their Zeeman components was investigated in a weak magnetic field. A fit of the zero field and Zeeman data yielded the relevant constants for the nuclear magnetic and electric quadrupole hyperfine interactions as well as the pertinent g-factors in each species. In the case of OD, the hf parameters agree well with those reported previously but are more accurately defined. For Ar•OD the previously unknown hyperfine and spin-rotation parameters of the A 2 ⌺ ϩ state were determined. A comparison of the hf parameters in the two systems allowed assessment of the effect of van der Waals complex formation on the electron distribution. Thus complexation is found to reduce the unpaired electron density on the deuteron by 7% which is indicative of significant chemical bonding between the Ar atom and the OD moiety in the A 2 ⌺ ϩ state of Ar•OD. For both systems, the g-factors g S and g l obtained suggest an admixture of other, possibly quartet, electronic states into the A 2 ⌺ ϩ state.

Collisional depolarization of OH(A) studied by Zeeman quantum beat spectroscopy

“…This was found on average to be 8.6% of the total signal intensity, qualitatively in line with previous measurements by various experimental groups [10,15,26,28,29]. A C parameter of this magnitude is also in reasonable agreement with predictions from the (1þ1) line-strength theory of Kummel et al [59], which predicts oscillations with an amplitude of 8.1% averaged over the three transitions employed.…”

“…However, the signal-to-noise ratios they obtained were relatively low, and it was only with the use of pulsed tunable dye laser radiation [5] that QBS started to find numerous applications. Since then, quantum beats have been observed in diatomics [6], triatomics [7], stable [8,9] and unstable polyatomics [10,11], as well as in condensed matter, for example, in semiconductors [12]. QBS has been employed to determine structural properties such as the electric dipole moment of the electronically excited state [13] (and more recently of excited vibrational levels of the ground electronic state [14]), hyperfine constants [15], spin-orbit matrix elements and asymmetry-splittings (see [16] and references therein), and quantities relevant to both intramolecular [17,18] and intermolecular dynamical processes [19,20].…”

“…Most studies exploiting Zeeman quantum beat spectroscopy (ZQBS) have concentrated on the information contained in the Lande´g factor, which is determined from the Larmor frequencies measured for known field strengths. There are many examples in the literature in which energy level splittings and hyperfine coupling constants for both atomic and molecular fragments have been determined from a knowledge of this parameter [6,7,10,15,19,[23][24][25][26][27][28][29]. Brucat and Zare [7,19] and, more recently, Xin and Reid [24,25], have presented studies on the fine and hyperfine structure of NO 2 .…”

“…Wallenstein et al [6] reported the observation of Zeeman quantum beats in molecular iodine as far back as 1974, their measurement aiding spectral assignment and permitting the determination of state-resolved Lande´g factors. The literature is also rich in studies on OH and OD fine and hyperfine structure [10,15,[26][27][28][29] using this method. In all of these cases, as in the above work on NO 2 [7,19,24,25], spectroscopic parameters have been determined with remarkable precision, highlighting the power of the ZQBS technique.…”

Precision spectra of AΣ+2 , v′=0

“…The previous best values of the A-X transition frequencies in OH and OD come from Stark et al [8], as well as from two earlier papers by Coxon [6,7]. Additionally, for OH, ter Meulen et al [18] have measured several of the A-state spin-rotation splittings with high precision using microwave double-resonance spectroscopy, and for OD, numerous authors have measured the A-state hyperfine splittings [19][20][21]. Since we have only been able to measure transitions to the lowest rotational states, we have augmented our effective Hamiltonian fits with information from these previous works, which include transitions to higher rotational levels.…”