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Abstract: We used the NIRSPEC instrument on the Keck-2 telescope atop Mauna Kea, HI to observe Comet C/2001 A2 (LINEAR) in a Target of Opportunity campaign on UT 2001 July 9.5, 10.5 August 4.4, 10.5. We measured seven organic parent volatiles (C2H6, C2H2, HCN, CH4, CO, CH3OH, H2CO) simultaneously with H2O. We obtained absolute production rates and relative abundances for parent volatiles, and also measured rotational temperatures for several of these species. The chemical composition of C/2001 A2 differs substantially from any comet we have observed to date. The abundances we measure (relative to H2O) for C2H6, C2H2, HCN, and CH3OH are enriched by a factor of ∼2 to 3 in C/2001 A2 compared with most comets in our database. Other molecular species were detected within the typical range of measured abundances. C/2001 A2 presented a unique opportunity to study the chemistry of a fragmenting comet where pristine areas are exposed to the Sun. [Copyright &y& Elsevier]

Abstract: NQR detection of materials, such as TNT, is hindered by the low signal-to-noise ratio at low NQR frequencies. Sweeping small (0–26mT) magnetic fields to shift the 1H NMR frequency relative to the 14N NQR frequencies can provide a significant increase of the 14N NQR signal-to-noise ratio. Three effects of 1H–14N level crossing are demonstrated in diglycine hydrochloride and TNT. These effects are (1) transferring 1H polarization to one or more of the 14N transitions, including the use of an adiabatic flip of the 1H polarization during the field sweep, (2) shortening the effective 14N T 1 by the interaction of 1H with the 14N transitions, (3) “level transfer” effect where the third 14N (spin 1) energy level or other 14N sites with different NQR frequency are used as a reservoir of polarization which is transferred to the measured 14N transition by the 1H. The 14N NQR signal-to-noise ratio can be increased by a factor of 2.5 for one 14N site in diglycine hydrochloride (and 2.2 in TNT), even though the maximum 1H frequency used in this work, 1116kHz, is only 30% larger than the measured 14N frequencies (834kHz for diglycine hydrochloride and 843kHz for TNT). [Copyright &y& Elsevier]

[Display omitted] • Spin-locked signal calculated for spin-3/2 nuclear quadrupole resonance NQR. • Using a powder sample, first direct NQR detection of 39 K in potassium chlorate. • Time constants, T 1 , T 2 e and T 2 * , were measured to determine detectability. • Optimal tip-angles for excitation and refocusing pulses compared to theory. • The resonance-frequency dependence on sample temperature was found. A model was developed for predicting a locked signal under a series of refocusing pulses for Nuclear Quadrupole Resonance (NQR) of spin I = 3 2 and tested with a powder of KClO 3. This work represents the first direct NQR detection of the 39 K line of potassium chlorate. The characteristic time constants, T 1 , T 2 e and T 2 ∗ , were measured to determine the detectability of potassium chlorate via 39 K-NQR. The echo train T 2 e was found to be strongly dependent on the refocusing pulse-spacing and weakly dependent on the refocusing pulse strength. The optimal angles of the excitation and echo pulse for a pulse train were also determined, as well as, the resonance-frequency dependence on sample temperature. [ABSTRACT FROM AUTHOR]

Abstract: The nucleus of Comet C/2001 A2 (LINEAR) split several times during its recent apparition, presenting an unusual opportunity to search for chemical differences in freshly exposed material. We conducted this search using NIRSPEC at the W.M. Keck Observatory on four dates in 2001: 9.5 and 10.5 July and 4.4 and 10.5 August. We detected the R0 and R1 lines of the vibrational band of CH4 near 3.3 μm on all dates. The R2 line was detected on 4.4 and 10.5 August. When we compare production rates of CH4 to H2O, we find evidence of a significant enhancement in August relative to that found in July. H2CO was securely detected via its and bands on 9.5 July. On 10.5 July, H2CO emission was much weaker, and its mixing ratio had dropped by a factor of about four. The mixing ratios for other detected volatile species did not change significantly over the course of the observations. We discuss the implications of this evidence for chemical heterogeneity in the nucleus of Comet C/2001 A2. [Copyright &y& Elsevier]

Multiple non-resonance fluorescence lines of water (H2O) were detected in Comet 153/P Ikeya–Zhang (2002 C1) between UT 2002 March 21.9 (Rh=0.51 AU) and April 13.9 (Rh=0.78 AU), using the Cryogenic Echelle Spectrometer (CSHELL) at the NASA Infrared Telescope Facility. Analysis of 2.9-μm water lines enabled accurate determination of rotational temperatures on three dates. The derived H2O rotational temperatures were 138+6−5, 141+10−9, and 94±3 K on UT 2002 March 22.0, March 23.0, and April 13.8, respectively. Water production rates were retrieved from spectral lines measured in nineteen separate grating settings over seven observing periods. The derived heliocentric dependence of the water production rate was Q=(9.2±1.1)×1028[Rh(−3.21±0.26)] molecules s−1. The spatial distribution of H2O in the coma was consistent with its release directly from the nucleus (as a native source) on all dates. [Copyright &y& Elsevier]

Graphical abstract Highlights • Atomic magnetometer array demonstrates interference rejection by factor of 120–250. • Phase-encoded reference signal used for real-time correction of unshielded signals. • Reference calibration depends on 87 Rb polarization, RF pulse duration & direction. • RF pulses orthogonal to pump and probe beams provide robust ESR calibration. Abstract An unshielded array of 87 Rb atomic magnetometers, operating close to 1 MHz, is used to attenuate interference by 42–48 dB. A sensitivity of 15 fT / Hz to a local source of signal is retained. In addition, a 2D spectroscopic technique, in which the magnetometers are repeatedly pumped and data acquired between pump times, enables a synchronously generated signal to be distinguished from an interfering signal very close in frequency; the timing and signal mimics what would be observed in a magnetic resonance echo train. Combining the interference rejection and the 2D spectroscopy techniques, a 100 fT local signal is differentiated from a 20 pT interference signal operating only 1 Hz away. A phase-encoded reference signal is used to calibrate the magnetometers in real time in the presence of interference. Key to the strong interference rejection is the accurate calibration of the reference signal across the array, obtained through electron spin resonance measurements. This calibration is found to be sensitive to atomic polarization, RF pulse duration, and direction of the excitation. The experimental parameters required for an accurate and robust calibration are discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Quantum magnetometer rapidly tuned for interleaved detection of different materials. • NQR detection time halved for 14 N in ammonium nitrate and 39 K in potassium chlorate. • Doubly resonant tank circuit designed and constructed for two-frequency excitation. • Explosives localized with a pair of 87 Rb multi-pass magnetometers. • Sensitivity in an unshielded environment compared with conventional coil detection. Interleaved Nuclear Quadrupole Resonance (NQR) detection was conducted on ammonium nitrate and potassium chlorate using two 87 Rb magnetometers, where potassium chlorate is measured during the T 1 limited recovery time of ammonium nitrate. The multi-pass magnetometers are rapidly matched to the NQR frequencies, 531 kHz and 423 kHz, with the use of a single tuning field. For ease of implementation, a double resonant tank circuit was used for excitation, but could be replaced by a broad-band transmitter. All work was done in an unshielded environment and compared to conventional coil detection. The two magnetometers were sensitive, base noise as low as 2 fT / Hz , and were shown to reduce ambient noise through signal subtraction. When an excitation pulse was introduced, however, residual ringing increased the noise floor; mitigation techniques are discussed. The two detection techniques resulted in comparable Signal-to-Noise Ratio (SNR). Interleaved detection using the atomic magnetometers took half the time of conventional detection and provided localization of the explosives. [ABSTRACT FROM AUTHOR]

Abstract: We investigated the parent volatile composition of the Oort cloud Comet C/2000 WM1 (LINEAR) on 23–25 November 2001, using the Near Infrared Echelle Spectrograph on the Keck II telescope. Flux-calibrated spectra, absolute production rates, and mixing ratios are presented for H2O, HCN, CH4, C2H2, C2H6, H2CO, CH3OH and CO. Compared with “organics-normal” comets, WM1 is moderately depleted in HCN, CH4 and CH3OH, and is even more depleted in C2H2 and CO. Its composition is thus intermediate to comets that are severely depleted in their organic volatile composition and those that exhibit “normal” organic volatile abundances. We argue that WM1 may have formed closer to the young Sun than “organics-normal” comets, but at greater distance than the severely depleted comets, before its ejection to the Oort cloud. The mixing ratios of the above-listed organic volatiles agree day-by-day for 23–25 November 2001. Thus, there is no evidence of macroscopic heterogeneity in chemistry of this comet’s nucleus at the achieved measurement accuracy. As the first comet to show moderate organic depletion in parent volatiles, WM1 represents an important addition to the emerging taxonomic classification based on chemical composition. [Copyright &y& Elsevier]

Abstract: We report the first detection of a spin echo after excitation of a powder sample by a single pulse at the resonance frequency during nuclear quadrupole resonance (NQR). These echoes can occur in samples that have an inhomogeneously broadened line, in this case due to the distribution of electric field gradients. The echoes are easily detectable when the Rabi frequency approaches the linewidth and the average effective tipping angle is close to 270°. When limited by a weak radio-frequency field, the single-pulse echo can be used to increase the signal to noise ratio over conventional techniques. These effects can be used to optimize the NQR detection of contraband containing quadrupole nuclei and they are demonstrated with glycine hemihydrochloride and hexhydro-1,3,5-trinitro-1,3,5-triazine (RDX). [Copyright &y& Elsevier]

Abstract: The Deep Impact encounter with the Jupiter family Comet 9P/Tempel 1 on UT 2005 July 4 was observed at high spectral resolving power () using the cross-dispersed near-infrared echelle spectrometer (NIRSPEC) at Keck-2. We report the temporal evolution of parent volatiles and dust (simultaneously measured) resulting from the event. Column abundances are presented for H2O and C2H6 beginning 30 min prior to impact and ending 50 min following impact , and for H2O and HCN from until , in time steps of approximately 6 min post-impact. The ejecta composition was revealed by an abrupt increase in H2O and C2H6 near . This showed C2H6/H2O to be higher than its pre-impact value by a factor , while HCN/H2O was unchanged within the uncertainty of the measurements. The mixing ratios for C2H6 and HCN in the ejecta agree with those found in the majority of Oort cloud comets, perhaps indicating a common region of formation. The expanding dust plume was tracked by continuum measurements, both through the 3.5-μm spectral continuum and through 2-μm images acquired with the SCAM slit-viewing camera, and each showed a monotonic increase in continuum intensity following impact. A Monte Carlo model that included dust opacity was applied to the dust coma, and its parameters were constrained by observations; the simulated continuum intensities reproduced both spectral and SCAM data. The relatively sudden appearance of the volatile ejecta signature is attributed to heating of icy grains (perhaps to a threshold temperature) that are decreasingly shadowed by intervening (sunward) dust particles in an optically thick ejecta plume, perhaps coupled with an accelerated decrease in dust optical depth near . [Copyright &y& Elsevier]

Abstract: The Deep Impact encounter with the Jupiter family Comet 9P/Tempel 1 on UT 2005 July 4 was observed at high spectral resolving power () using the cross-dispersed near-infrared echelle spectrometer (NIRSPEC) at Keck-2. We report the temporal evolution of parent volatiles and dust (simultaneously measured) resulting from the event. Column abundances are presented for H2O and C2H6 beginning 30 min prior to impact and ending 50 min following impact , and for H2O and HCN from until , in time steps of approximately 6 min post-impact. The ejecta composition was revealed by an abrupt increase in H2O and C2H6 near . This showed C2H6/H2O to be higher than its pre-impact value by a factor , while HCN/H2O was unchanged within the uncertainty of the measurements. The mixing ratios for C2H6 and HCN in the ejecta agree with those found in the majority of Oort cloud comets, perhaps indicating a common region of formation. The expanding dust plume was tracked by continuum measurements, both through the 3.5-μm spectral continuum and through 2-μm images acquired with the SCAM slit-viewing camera, and each showed a monotonic increase in continuum intensity following impact. A Monte Carlo model that included dust opacity was applied to the dust coma, and its parameters were constrained by observations; the simulated continuum intensities reproduced both spectral and SCAM data. The relatively sudden appearance of the volatile ejecta signature is attributed to heating of icy grains (perhaps to a threshold temperature) that are decreasingly shadowed by intervening (sunward) dust particles in an optically thick ejecta plume, perhaps coupled with an accelerated decrease in dust optical depth near . [Copyright &y& Elsevier]

Abstract: We obtained high-resolution () spectra of Comet C/1999 H1 (Lee) on UT 1999 August 19.6 and 21.6 using the cross-dispersed Near InfraRed SPECtrometer (NIRSPEC) at the Keck Observatory atop Mauna Kea, HI. Here we present spectra of Comet Lee between 2.874 and 3.701 μm (3479–2702 cm−1) representing the most complete high-resolution infrared survey of a comet to date in this wavelength region. Using published line lists and laboratory spectra we have identified 444 of the 545 distinct emission features present in these spectra. We have tabulated the rest frequencies, assignments, relative intensities, and signal-to-noise ratios of all detected emissions. In addition to gaining insights into the chemistry of Comet Lee, this survey provides a valuable tool for planning future high-resolution infrared observations of comets and other astronomical targets, and for retrospective comparison to existing high-resolution infrared datasets. [Copyright &y& Elsevier]

We present absolute abundances and latitudinal variations of ozone and water in the atmosphere of Mars during its late northern spring (Ls=67.3°) shortly before aphelion. Long-slit maps of the a1Δg state of molecular oxygen (O2) and HDO, an isotopic form of water, were acquired on UT January 21.6 1997 using a high-resolution infrared spectrometer (CSHELL) at the NASA Infrared Telescope Facility. O2(a1Δg) is produced by ozone photolysis, and the ensuing dayglow emission at 1.27 μm is used as a tracer for ozone. Retrieved vertical column densities for ozone above ∼20 km ranged between 1.5 and 2.8 μm-atm at mid- to low latitudes (30°S–60°N) and decreased outside that region. A significant decrease in ozone density is seen near 30°N (close to the subsolar latitude of 23.5°N). The rotational temperatures retrieved from O2(a–X) emissions show a mean of 172±2.5 K, confirming that the sensed ozone lies in the middle atmosphere (∼24 km). The ν1 fundamental band of HDO near 3.67 μm was used as a proxy for H2O. The retrieved vertical column abundance of water varies from 3 precipitable microns (pr-μm) at ∼30°S to 24 pr-μm at ∼60°N. We compare these results with current photochemical models and with measurements obtained by other methods. [Copyright &y& Elsevier]

• Homogeneous fields are designed by expanding both surface current and magnetic field. • The method is useful in situations where unconventional geometries are needed. • Warping due to curing limited the utility of 3D printing technology for this method. • Homogeneity of 30 ppm was achieved for a half meter linear array of magnetometers. In low-field magnetic resonance applications there is often an interest in creating homogeneous magnetic fields over unusual geometries, particularly when quantum magnetometers are involved. In this paper a design method is proposed, where both the surface current and magnetic field are expanded to find current coefficients that cancel out higher order field terms. Two coils are designed using this double expansion methodology: (1) a tuning field for a half-meter-long atomic magnetometer array and (2) a null field for a magnetometer to operate adjacent to an excitation solenoid. The field verification of the former shows the accuracy of CNC milling and the method proposed; a close analysis of the field signature in the latter revealed the limitations of 3D printing for precise scientific applications. Both coils are designed to be fifth-order error systems or better. [ABSTRACT FROM AUTHOR]