Passion for precision.

Optical frequency combs from mode-locked femtosecond lasers have revolutionized the art of counting the frequency of light. They can link optical and microwave frequencies in a single step, and they provide the long missing clockwork for optical atomic clocks. By extending the limits of time and frequency metrology, they enable new tests of fundamental physics laws. Precise comparisons of optical resonance frequencies of atomic hydrogen and other atoms with the microwave frequency of a cesium atomic clock are establishing sensitive limits for possible slow variations of fundamental constants. Optical high harmonic generation is extending frequency comb techniques into the extreme ultraviolet, opening a new spectral territory to precision laser spectroscopy. Frequency comb techniques are also providing a key to attosecond science by offering control of the electric field of ultrafast laser pulses. In our laboratories at Stanford and Garching, the development of new instruments and techniques for precision laser spectroscopy has long been motivated by the goal of ever higher resolution and measurement accuracy in optical spectroscopy of the simple hydrogen atom which permits unique confrontations between experiment and fundamental theory. This lecture recounts these adventures and the evolution of laser frequency comb techniques from my personal perspective.     

The A. J. P. Martin award recipients for 1988

The A. J. P. Martin award recipients for 1988     

Sieve-based device for MALDI sample preparation. III. Its power for quantitative measurements

The solid sample inhomogeneity is a weak point of traditional MALDI deposition techniques that reflects negatively on quantitative analysis. The recently developed sieve-based device (SBD) sample deposition method, based on the electrospraying of matrix/analyte solutions through a grounded sieve, allows the homogeneous deposition of microcrystals with dimensions smaller than that of the laser spot. In each microcrystal the matrix/analyte molar ratio can be considered constant. Then, by irradiating different portions of the microcrystal distribution an identical response is obtained. This result suggests the employment of SBD in the development of quantitative procedures. For this aim, mixtures of different proteins of known molarity were analyzed, showing a good relationship between molarity and intensity ratios. This behaviour was also observed in the case of proteins with quite different ionic yields. The power of the developed method for quantitative evaluation was also tested by the measurement of the abundance of IGPP[Oxi]GPP[Oxi]GLMGPP (m/z 1219) present in the collagen-α-5(IV) chain precursor, differently expressed in urines from healthy subjects and diabetic-nephropathic patients, confirming its overexpression in the presence of nephropathy. The data obtained indicate that SBD is a particularly effective method for quantitative analysis also in biological fluids of interest.     

A BSSE-free SCF algorithm for intermolecular interactions. IV. Generalization for open-shell systems

The simple and efficient a priori BSSE-free SCF method (CHA/F) proposed in the previous parts of this series is extended to the case of open-shell systems treated at the single-determinant UHF level of theory. The appropriate equations were derived and sample calculations are presented on three different (H₃⁺(DOTTED BOND)H, H₂O(DOTTED BOND)H, and CH₄(DOTTED BOND)H) systems. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 68: 151–158, 1998     

E.S.R. of hydrazoxyl radicals: Evidence for conformational isomers.

Thermolysis of azocarboxylates has been investigated by e.s.r. Experimental evidence for the existence of conformational isomerism in acylnitroxides has been obtained.