The seven independent adiabatic elastic constants of CaWO₄ are calculated using Born's longwave method and the rigid ion model of Steinman et al. (1972). Good agreement exists between the calculated elastic constants and those measured by Gluyas et al. (1973). The sign of C₁₆ is consistent with the observation of Farley et al. (1972). Further the dynamical equilibrium conditions are also found to be satisfied for this model.

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The energy levels of the 4I ground term of Er³⁺ in single crystals of CaWO₄ were established by absorption and fluorescence spectra measurements. The measurements were made using crystals at temperatures of 2, 20, and 85°K. The energy level scheme allows an interpretation of the 1.612‐μ four‐level CaWO₄:Er³⁺ laser transition and shows the terminal energy level of this transition to be 318 cm⁻¹ above the ground state rather than 375 cm⁻¹ as reported by Kiss and Duncan. An effective Hamiltonian of the form suggested by Karayianis was diagonalized in a basis of Russell–Saunders wavefunctions to obtain the calculated energy levels and wavefunctions for the entire ground term of Er³⁺. The calculation takes into account the complete J mixing of the states within the ground term and is equivalent to determining the effects of the spin–orbit interaction to better than second order. An rms deviation of 18 cm⁻¹was found as the best agreement between the calculated and experimental energy levels using the Hamiltonian: H = λ1(L⋅S) + λ2(L⋅S)2 + λ3(L⋅S)3 + ΣlmB†lmClm. The empirically determined parameters are (in cm⁻¹) λ1 = − 613, λ2 = − 19.3, λ3 = − 0.499, B20 = 404, B40 = − 685, B60 = 12.4, B44 = 728,ReB64 = 452, and ImB64 = 164. Using wavefunctions determined with these parameters, the g factors were calculated for the states of the ground term. The calculated and measured g factors for the two lower energy states are in good agreement where the calculated values are g‖(ground state) = 1.265, g⊥(ground state) = 8.487, g‖* (first excited state) = 3.22, and g⊥* (first excited state) = 7.06, and the measured values in the same order are g‖ = 1.247, g⊥ = 8.400, g‖* = 3.42, and g⊥* = 6.98. A Γ5,6ground statewavefunction is compatible with the results obtained here, whereas a Γ7,8ground statewavefunction is not. Previous studies had not established the ground statewavefunction uniquely.

 

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The e.p.r. spectrum of (ReO₄)O^2- in CaWO₄ has been measured in the temperature 4-120 K as a function of orientation. The spectrum including many forbidden lines may be fitted to the spin Hamiltonian H = μ _BB\cdot g\cdot S\cdot +I\cdot tilde{A}\cdot S\cdot +I\cdot tilde{P}\cdot I\cdot in tetragonal form with S = 1/2 and I=5/2. At 4.2 K, endor measurements for the magnetic field oriented parallel to the unique axis, taken in conjunction with the e.p.r. spectrum, yield spin Hamiltonian parameters g_\| = 1.8549 ± 0.0002, g_perp = 1.7164 ± 0.0002, A_perp = (±)(42± 2)× 10^-4 cm ^-1, A_perp = (±)(324± 2)× 10^-4 cm ^-1 and P_\| = (mp)(5± 3)× 10^-4 cm ^-1, with g_N = (±) 1.27 for the ¹⁸⁷Re nuclide. These parameters are consistent with the single electron occupying the |3z² - r²> orbital of a 5d¹ ion. The e.p.r. linewidth, which is strongly sensitive to both orientation and temperature, has been examined in detail. Preliminary studies of the relaxation properties of the centre are discussed in qualitative terms.

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Tungsten is an extremely dense metal, heavier than lead. It is also very durable, so a high-density tungsten dart resists wear and the grip will last much longer. On softer metal darts, the grooves and rough knurling may wear down fairly quickly from skin acid, friction, and hitting other darts. Originally tungsten was only a small percentage of the dart barrel (40 - 50%), today most tungsten darts are between 80 and 95% tungsten.

Today let’s learn some glossaries of tungsten dart from R to X!

-R-
REDEEMER - A dart, (often a T20) that "redeems" two previous poor efforts.

RIGHT CHURCH - Term for hitting a double or triple, but the wrong number. Also known as "DADDY'S BED"

ROBIN HOOD - When you shoot a dart into the shaft of another.

ROUND OF NINE - Throwing three triples in one turn in Cricket.

ROUND THE CLOCK - Any of a number of game variants where players compete to be the first to hit all the sectors on the dartboard in an agreed order (usually numerical), finishing with the outer bull followed by the bull. In some versions hitting a double entitles the player to skip the next number, with a treble entitling the player to skip two numbers. Also commonly played by single players as a form of practice.

-S-
SCROAT - A dart that is aimed for treble 20, but ends up in double 20.

SET - A scoring method used in many tournaments.

SHAFT - The middle section of the darts that holds the Flight.

SHANGHAI - A score of a single, double and triple in the same number. "Shanghai" sometimes refers to a checkout of 120 (single, treble and double 20, also as "Shanghai 20"). In some games this is an automatic win. This is also the name of a game.

SHARKEY - A non-registered player who has to assume a false identity in order to fill in for an absent player in a league game, e.g. "due to poor turnout, The Arms had to use a Sharkey".

SHUT OUT - When you lose a game without ever scoring in it.

SINGLE BULL - On dartboards configured with a bullseye consisting of two concentric circles, the outer circle is commonly green and worth 25 and the inner circle is commonly red and worth 50 points. Hitting the outermost ring of this type of bullseye is a "SINGLE-BULL". (See also: "BULLSEYE")

SKUNKED - When you lose a game without ever scoring in it.

SLOP - Darts that score, but not where you wanted them.

SPIDER - The metal web that divides the dartboard into sections.

SPLASH - Darts that score, but not where you wanted them.

SPRAY 'N' PRAY - Darts thrown by an irate and less talented player, rather quickly

STICKS - The darts themselves.

STRAIGHT IN - A game that requires no special shot to begin scoring.

STRIKING OIL - Hitting a double bull when 'diddling for the middle' - comes from the black centre of some modern dart boards.

-T-
THREE IN A BED - Three darts in the same triple of a number. i.e. three triple 20's 180!

THROW LINE - The line you stand behind and throw the darts from.

TOE LINE - The line you stand behind and throw the darts from.

TON - A score of 100 in a game of x01. Scores over 100 would be called a "ton-whatever" for example, a ton-thirty would be a score of 130.

TON OF NAILS - A score of 5 where all three darts fell in the 1 bed with 1 dart in the treble 1.

TOP BANANA - Double 20. Usually exclaimed after hitting this bed to win a match.

TOP OF THE BOARD - The numbers on the top half of the dartboard.

TOPS - The double 20 bed. As in "he wants tops for the match".

TRIPLE/TREBLE - The thin inner ring of the dartboard, it usually counts for three times the number hit.

-U-
UPSTAIRS - The upper half of the dartboard

-W-
WET FEET - Standing too close to the dartboard (that is, in front of the toe line).

WEDGE - A section or sections of the dartboard.

WHITE HORSE - Scoring three virgin (untouched) triples in Cricket.

WIRE - Darts that just miss where you aimed but on the other side of the spider.

-X-
X - A double-one out

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